assignment of an object of class null is not valid

ReSharper 2024.1 Help

Code inspection: possible 'null' assignment to non-nullable entity.

Category : Constraints Violations

ID : AssignNullToNotNullAttribute

EditorConfig : resharper_assign_null_to_not_null_attribute_highlighting

Default severity : Warning

Language : C#

Requires SWA : No

The [NotNull] attribute introduces a contract to indicate that a particular symbol can never be null.

As the [NotNull] can be used nearly everywhere, there are different situations where this inspection can help you find violations of contracts that [NotNull] brings. Here are a couple of examples:

[NotNull] helps use your symbols marked accordingly without additional null checks.

However, when you mark your public members with [NotNull] , you have to make sure that they actually never return null. As soon as the annotation is there, ReSharper will check if this contract is valid:

[NotNull] can also serve as a contract for parameters, for example if you check the parameter and throw ArgumentNullException if null is passed. In this case, ReSharper will warn users of your method if they try to pass null value to the annotated parameter:

Note that this inspection will is not limited to symbols marked with NotNull in your source code. This annotation can also be added via external annotations , and it is already there for related symbols in the .NET Framework Class Library and other frequently used libraries, as external annotations for these libraries are included in the ReSharper installation.

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Weirdness with and without []: assignment of an object of class "numeric" is not valid for slot "values" in an object of class.

The following indicates that assignment of numeric values to an @values part of an mxMatrix only works when the [] are there. When they are not there (which used to work fine) we get an error:

> DirectionofCausationBcausesA$ACE.B@values [,1] [,2] [1,] 0 0 [2,] 0 0 > DirectionofCausationBcausesA$ACE.B@values[] [,1] [,2] [1,] 0 0 [2,] 0 0 > > DirectionofCausationBcausesA$ACE.B@values<-0 Error in checkSlotAssignment(object, name, value) : assignment of an object of class "numeric" is not valid for slot "values" in an object of class "FullMatrix"; is(value, "matrix") is not TRUE > > > DirectionofCausationBcausesA$ACE.B@values [,1] [,2] [1,] 0 0 [2,] 0 0 > > DirectionofCausationBcausesA$ACE.B@values[]<-0

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This is not a bug. The slots of a S4 object are typed objects. They are possibly the only objects in R that are typed objects. '0' is a numeric vector, while ACE.B@values expects a matrix type. Therefore the assignment ACE.B@values[] <- 0 is necessary.

An analogy would be:

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Check if any of class properties is not null/empty/was assigned

I have a class that I use to display on a web page fieldset. However, all of the properties of this class are optionally filled in by the user, which means all of them could be null/default. In this case I would like not to render the fieldset at all, instead of displaying an empty one.

I wrote a simple isEmpty() method that checks all property values using reflection, but I'm afraid this may become way too expansive.

The isEmpty() , of course, assumes all properties are strings.

What do you think? Will this become potentially expansive as the class grows?

• 1 \$\begingroup\$ Well, to start, I think I'd rather see the method named IsEmpty instead of isEmpty . This is per Microsoft's Capitalization Guideline . \$\endgroup\$ –  RubberDuck Nov 19, 2014 at 21:36
• \$\begingroup\$ Is this ASP.NET MVC 5? \$\endgroup\$ –  mjolka Nov 19, 2014 at 23:01

2 Answers 2

Don't use variable names such as t . They're not meaningful, not for you, not for others. In this case, use type .

Class names, public fields and method names use PascalCase and not camelCase . So, isEmpty will become IsEmpty . But then again, this is also not a meaningful name. Boolean methods or properties in C# will most likely start with Is or Has . An example for the name of your method would be HasAllEmptyProperties .

var keyword:

Use var to declare your variables instead of declaring them explicitly. The compiler will determine the type for you and your code looks cleaner.

The method:

Your code looks good. You could however make it cleaner by using LinQ. Loops won't be avoided but it looks cleaner. I'm not saying this is a perfect solution but here goes:

I could also have used the All() method and positive comparison instead of Any() . But this is inefficient as all elements have to be checked against the condition whereas Any() will return as soon as an element satisfies the condition (like in your loop).

You can take the comparison code and throw it in an extension method for reusability. It also makes your method-code cleaner, for example:

Since you only have two properties, performace won't be a problem. Even if you were to add a couple more properties. Hope this helps!

• \$\begingroup\$ Thanks for your reply. I agree with you on the variable name; however, I chose "t" for "Type". I don't think it is a problem in this particular case because the code is really small (it is not a habit). As for the styling, I have only recently started to use C#, and the style is a bit different from other languages I'm familiar with, and sometimes I mix them up. Thanks for pointing it out. Regarding the var, I did use it. I kept "Type" because it is one letter longer, it's not a real time saver to type "var" instead. Had I used var, I would definitely have named it "type" instead of "t". \$\endgroup\$ –  victor Nov 20, 2014 at 4:49
• \$\begingroup\$ About using LINQ, in this case, I disagree that it makes the code easier to read. I think it makes the code looks a lot more like code instead of a human readable text (again, in this case). The extension method is interesting, never used any extension method, I will look into it; still, this method is used only for this class and wont every be used by any other, so I think I will skip that :) Thanks for your review. --Edit-- I just checked, LINQ would probably be slower than foreach. \$\endgroup\$ –  victor Nov 20, 2014 at 4:52
• 1 \$\begingroup\$ As I said, your code looks good as it is. The LinQ option was just another way of achieving the same result. I've worked quite a bit with it so for me it's very readable. The extension method might indeed be overkill but it's a nice feature and I always have expansion in mind. That's why I often use (extension) methods. \$\endgroup\$ –  Abbas Nov 20, 2014 at 7:08

It looks rather hacky because I have the feeling there must be someplace down the line where you can more easily determine whether or not the properties are filled in.

Nevertheless: right now your code will only work for strings while it is probably realistic to say that there might be other fields in the future as well (Id, DateOfBirth, etc) which would require a code change. Therefore I would suggest making your code a little less string-specific:

• Using default so it words with primitive types (they won't be able to be 0 with this)
• If you do want to be able to be 0 , make them nullable types instead
• as combined with != null
• IsNullOrWhiteSpace(string) instead of comparison to empty quotes
• Removed t since it was only used once

• \$\begingroup\$ Thanks for the stackoverflow link. It looks hacky for me too, that's why I posted it here; however, the fact is that there is no place down the line where it would be easier to check the props because I need to check all of them, and without reflection there is no way to know which properties the class has, except by hard coding them "x.name not null && x.lastname not null etc"... does isNullOrWhiteSpace fails for empty string as well? \$\endgroup\$ –  victor Nov 20, 2014 at 14:07
• 1 \$\begingroup\$ I figured maybe you could check the ModelState somewhere combined with [Required] attributes, but that depends on your situation of course. Yes, it does . \$\endgroup\$ –  Jeroen Vannevel Nov 20, 2014 at 14:09

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I’m trying to use the new version of topGO but R gives me an error that I’m not able to correct

Using the toy dataset I’m building the topGOdata object using annFUN.org as annotation

GOdata <- new("topGOdata", ontology = "BP", allGenes=geneList, annot = annFUN.org, mapping=org.Hs.eg, ID="Gene Symbol")

and I get this error:

Building most specific GOs ..... Error in as.character(x) : cannot coerce type 'closure' to vector of type 'character'

How can I solve that? I don’t have this error when I use annFUN.gene2GO as annotation

The error possibly relates to how you produced annFun.org , even though no error was returned when you ran the annFUN.org() command. Also, the mapping is usually specified, not in new() , but, rather, in annFUN.org() as mapping = 'org.Hs.eg.db' .

In addition, just to be sure, geneList should be a named numeric vector, usually of p-values, whose names relate to genes. In your case, they have to be gene symbols.

Finally, I think that ID should be ID = 'symbol'

Here is an example:

I show this on Biostars: https://www.biostars.org/p/350710/#350712

thanks a lot, Kevin.

I used your code but I still don't menage to run TopGO.

Here my script where the input files are the list of universe genes (with ENSEMBLE id) and the list of relevant genes. So, I don't have any pvalue, only gene names in my files

At the end I got this error:

Hey again, the problem is that the value passed to geneSel should be a function - you are passing to it another named vector of values.

If you take a look at my code again, you'll see that I am passing the following function to geneSel :

This function will be applied to, in your case, the total.gene.names variable. It is essentially used to filter your input gene list by, for example, p-value < 0.05 (my function). Here is an example:

Thanks a lot for clarifying this.

I modified my code as:

I see - that may not function as expected because the selection function will only accept one parameter.

Just to recap: the object passed to allGenes should be a named vector of p-values or other values, such as fold changes. In your case, therefore, your total.gene.names variable should look something like this:

The function passed to geneSel will be applied to total.gene.names and should return a boolean vector of values.

In your case, you may want to use:

Then test it to see what it produces:

What is the output? - it should return a vector of TRUE | FALSE

This assumes that both total.gene.names significant.genes are named vectors of p-values or fold changes.

If you still have problems, you could post the output of total.gene.names and significant.genes

head(all.genes)

ENSG00000238009 ENSG00000157999 ENSG00000198157 ENSG00000227288 ENSG00000186831 ENSG00000226261

selection(all.genes) [1] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE

[13] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE

[25] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE

[37] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE

[49] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE

[61] TRUE TRUE TRUE TRUE TRUE TRUE TRUE FALSE FALSE FALSE FALSE FALSE

[73] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE .....

GOdata <- new('topGOdata', ontology = 'BP', allGenes = all.genes, annot = annFUN.GO2genes, GO2genes = allGO2genes, geneSel = selection(all.genes), nodeSize = 10)

assignment of an object of class “logical” is not valid for @‘geneSelectionFun’ in an object of class “topGOdata”; is(value, "function") is not TRUE Calls: go.enrichment ... new -> initialize -> initialize -> .local -> <anonymous> Execution halted

Ah, this should now work:

I changed geneSel = selection(all.genes) to geneSel = selection

Build GO DAG topology .......... ( 0 GO terms and 0 relations. ) Error in if is.na(index) || index < 0 || index > length(nd)) stop("vertex is not in graph: ", : missing value where TRUE/FALSE needed Calls: go.enrichment ... buildLevels -> getGraphRoot -> sapply -> adj -> adj Execution halted

Ah, looks like you are using Ensembl gene IDs. So, you need to use:

Apparently it cannot read my genes...

**Annotating nodes ............... ( 12920 genes annotated to the GO terms. )

Warning message: In .local(object, test.stat, ...) : No enrichment can pe performed - there are no feasible GO terms!**

I think that it was able to read the genes but could not find any enriched term that passed the basic thresholds.

You could try to reduce the value of nodeSize to 5. Also, does anything come up for the other ontologies:

Otherwise, you may have to explore other tests other than Fisher's.

I usually run these functions like this:

If I use KS test I have the same warning message

• No enrichment can pe performed - there are no feasible GO terms!*

And it's not possible as I'm testing genes well known to belong to pathways related to lipids

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Working with objects

JavaScript is designed on a simple object-based paradigm. An object is a collection of properties , and a property is an association between a name (or key ) and a value. A property's value can be a function, in which case the property is known as a method .

Objects in JavaScript, just as in many other programming languages, can be compared to objects in real life. In JavaScript, an object is a standalone entity, with properties and type. Compare it with a cup, for example. A cup is an object, with properties. A cup has a color, a design, weight, a material it is made of, etc. The same way, JavaScript objects can have properties, which define their characteristics.

In addition to objects that are predefined in the browser, you can define your own objects. This chapter describes how to use objects, properties, and methods, and how to create your own objects.

Creating new objects

You can create an object using an object initializer . Alternatively, you can first create a constructor function and then instantiate an object by invoking that function with the new operator.

Using object initializers

Object initializers are also called object literals . "Object initializer" is consistent with the terminology used by C++.

The syntax for an object using an object initializer is:

Each property name before colons is an identifier (either a name, a number, or a string literal), and each valueN is an expression whose value is assigned to the property name. The property name can also be an expression; computed keys need to be wrapped in square brackets. The object initializer reference contains a more detailed explanation of the syntax.

In this example, the newly created object is assigned to a variable obj — this is optional. If you do not need to refer to this object elsewhere, you do not need to assign it to a variable. (Note that you may need to wrap the object literal in parentheses if the object appears where a statement is expected, so as not to have the literal be confused with a block statement.)

Object initializers are expressions, and each object initializer results in a new object being created whenever the statement in which it appears is executed. Identical object initializers create distinct objects that do not compare to each other as equal.

The following statement creates an object and assigns it to the variable x if and only if the expression cond is true:

The following example creates myHonda with three properties. Note that the engine property is also an object with its own properties.

Objects created with initializers are called plain objects , because they are instances of Object , but not any other object type. Some object types have special initializer syntaxes — for example, array initializers and regex literals .

Using a constructor function

Alternatively, you can create an object with these two steps:

• Define the object type by writing a constructor function. There is a strong convention, with good reason, to use a capital initial letter.
• Create an instance of the object with new .

To define an object type, create a function for the object type that specifies its name, properties, and methods. For example, suppose you want to create an object type for cars. You want this type of object to be called Car , and you want it to have properties for make, model, and year. To do this, you would write the following function:

Notice the use of this to assign values to the object's properties based on the values passed to the function.

Now you can create an object called myCar as follows:

This statement creates myCar and assigns it the specified values for its properties. Then the value of myCar.make is the string "Eagle" , myCar.model is the string "Talon TSi" , myCar.year is the integer 1993 , and so on. The order of arguments and parameters should be the same.

You can create any number of Car objects by calls to new . For example,

An object can have a property that is itself another object. For example, suppose you define an object called Person as follows:

and then instantiate two new Person objects as follows:

Then, you can rewrite the definition of Car to include an owner property that takes a Person object, as follows:

To instantiate the new objects, you then use the following:

Notice that instead of passing a literal string or integer value when creating the new objects, the above statements pass the objects rand and ken as the arguments for the owners. Then if you want to find out the name of the owner of car2 , you can access the following property:

You can always add a property to a previously defined object. For example, the statement

adds a property color to car1 , and assigns it a value of "black" . However, this does not affect any other objects. To add the new property to all objects of the same type, you have to add the property to the definition of the Car object type.

You can also use the class syntax instead of the function syntax to define a constructor function. For more information, see the class guide .

Using the Object.create() method

Objects can also be created using the Object.create() method. This method can be very useful, because it allows you to choose the prototype object for the object you want to create, without having to define a constructor function.

Objects and properties

A JavaScript object has properties associated with it. Object properties are basically the same as variables, except that they are associated with objects, not scopes . The properties of an object define the characteristics of the object.

For example, this example creates an object named myCar , with properties named make , model , and year , with their values set to "Ford" , "Mustang" , and 1969 :

Like JavaScript variables, property names are case sensitive. Property names can only be strings or Symbols — all keys are converted to strings unless they are Symbols. Array indices are, in fact, properties with string keys that contain integers.

Accessing properties

You can access a property of an object by its property name. Property accessors come in two syntaxes: dot notation and bracket notation . For example, you could access the properties of the myCar object as follows:

An object property name can be any JavaScript string or symbol , including an empty string. However, you cannot use dot notation to access a property whose name is not a valid JavaScript identifier. For example, a property name that has a space or a hyphen, that starts with a number, or that is held inside a variable can only be accessed using the bracket notation. This notation is also very useful when property names are to be dynamically determined, i.e. not determinable until runtime. Examples are as follows:

In the above code, the key anotherObj is an object, which is neither a string nor a symbol. When it is added to the myObj , JavaScript calls the toString() method of anotherObj , and use the resulting string as the new key.

You can also access properties with a string value stored in a variable. The variable must be passed in bracket notation. In the example above, the variable str held "myString" and it is "myString" that is the property name. Therefore, myObj.str will return as undefined.

This allows accessing any property as determined at runtime:

However, beware of using square brackets to access properties whose names are given by external input. This may make your code susceptible to object injection attacks .

Nonexistent properties of an object have value undefined (and not null ).

Enumerating properties

There are three native ways to list/traverse object properties:

• for...in loops. This method traverses all of the enumerable string properties of an object as well as its prototype chain.
• Object.keys() . This method returns an array with only the enumerable own string property names ("keys") in the object myObj , but not those in the prototype chain.
• Object.getOwnPropertyNames() . This method returns an array containing all the own string property names in the object myObj , regardless of if they are enumerable or not.

You can use the bracket notation with for...in to iterate over all the enumerable properties of an object. To illustrate how this works, the following function displays the properties of the object when you pass the object and the object's name as arguments to the function:

The term "own property" refers to the properties of the object, but excluding those of the prototype chain. So, the function call showProps(myCar, 'myCar') would print the following:

The above is equivalent to:

There is no native way to list inherited non-enumerable properties. However, this can be achieved with the following function:

For more information, see Enumerability and ownership of properties .

Deleting properties

You can remove a non-inherited property using the delete operator. The following code shows how to remove a property.

Inheritance

All objects in JavaScript inherit from at least one other object. The object being inherited from is known as the prototype, and the inherited properties can be found in the prototype object of the constructor. See Inheritance and the prototype chain for more information.

Defining properties for all objects of one type

You can add a property to all objects created through a certain constructor using the prototype property. This defines a property that is shared by all objects of the specified type, rather than by just one instance of the object. The following code adds a color property to all objects of type Car , and then reads the property's value from an instance car1 .

Defining methods

A method is a function associated with an object, or, put differently, a method is a property of an object that is a function. Methods are defined the way normal functions are defined, except that they have to be assigned as the property of an object. See also method definitions for more details. An example is:

where objectName is an existing object, methodName is the name you are assigning to the method, and functionName is the name of the function.

You can then call the method in the context of the object as follows:

Methods are typically defined on the prototype object of the constructor, so that all objects of the same type share the same method. For example, you can define a function that formats and displays the properties of the previously-defined Car objects.

Notice the use of this to refer to the object to which the method belongs. Then you can call the displayCar method for each of the objects as follows:

Using this for object references

JavaScript has a special keyword, this , that you can use within a method to refer to the current object. For example, suppose you have 2 objects, Manager and Intern . Each object has its own name , age and job . In the function sayHi() , notice the use of this.name . When added to the 2 objects, the same function will print the message with the name of the respective object it's attached to.

this is a "hidden parameter" of a function call that's passed in by specifying the object before the function that was called. For example, in Manager.sayHi() , this is the Manager object, because Manager comes before the function sayHi() . If you access the same function from another object, this will change as well. If you use other methods to call the function, like Function.prototype.call() or Reflect.apply() , you can explicitly pass the value of this as an argument.

Defining getters and setters

A getter is a function associated with a property that gets the value of a specific property. A setter is a function associated with a property that sets the value of a specific property. Together, they can indirectly represent the value of a property.

Getters and setters can be either

• defined within object initializers , or
• added later to any existing object.

Within object initializers , getters and setters are defined like regular methods , but prefixed with the keywords get or set . The getter method must not expect a parameter, while the setter method expects exactly one parameter (the new value to set). For instance:

The myObj object's properties are:

• myObj.a — a number
• myObj.b — a getter that returns myObj.a plus 1
• myObj.c — a setter that sets the value of myObj.a to half of the value myObj.c is being set to

Getters and setters can also be added to an object at any time after creation using the Object.defineProperties() method. This method's first parameter is the object on which you want to define the getter or setter. The second parameter is an object whose property names are the getter or setter names, and whose property values are objects for defining the getter or setter functions. Here's an example that defines the same getter and setter used in the previous example:

Which of the two forms to choose depends on your programming style and task at hand. If you can change the definition of the original object, you will probably define getters and setters through the original initializer. This form is more compact and natural. However, if you need to add getters and setters later — maybe because you did not write the particular object — then the second form is the only possible form. The second form better represents the dynamic nature of JavaScript, but it can make the code hard to read and understand.

Comparing objects

In JavaScript, objects are a reference type. Two distinct objects are never equal, even if they have the same properties. Only comparing the same object reference with itself yields true.

For more information about comparison operators, see equality operators .

• Inheritance and the prototype chain

Error in (function (cl, name, valueClass) :assignment of an object of class “numeric” is not vali...

Error in (function (cl, name, valueClass) : assignment of an object of class “numeric” is not valid for @‘data.signaling’ in an object of class “CellChat”; is(value, "AnyMatrix") is not TRUE

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assignment of an object of class null is not valid

I'm wrestling with tximport/DESeq2. I've create a small experiment dataset of 2 paired end fastq, generated counts with salmon, and successfully read them in with tximport (or so I think). "files" is my list of 2 quant.sf files. tx2gene is the obvious.

> dds <- DESeqDataSetFromTximport(txi, sampleTable, ~tissue) Error in checkSlotAssignment(object, name, value) :    assignment of an object of class "NULL" is not valid for slot 'NAMES' in an object of class "DESeqDataSet"; is(value, "characterORNULL") is not TRUE

I've just recently installed R 3.4.0 and have update all packages. I see that there was some changes in S4 of renaming characterORNULL to character_OR_NULL; is this the issue?

Hi Michael,

Thanks for the response.

biocLite() looks clean:

For a brief time, I thought my problem was that I was no pulling in tximportData. But adding that did not help.

Should I be concerned that the Class is -none- in the DESeqDataSet?

The error message almost makes sense if it's happening from trying to act on a null class.

Incidentally, I see that makeExampleDESeqDataSet() also returns the same error for me

That's useful for debugging, isolating the problem to DESeq2 or its depends. Can you call traceback() after the error and post here?

RangedSummarizedExperiment has character_OR_NULL and DESeq2 has characterORNULL. I thought the latter was obsolete. This is also the one that shows up in the error message.

I'm starting to get more suspicious of the change in the S4Vectors package. Renaming characterORNULL to character_OR_NULL happened in 0.14.0 9 days ago.

What is your version of S4Vectors?

Does BiocInstaller::biocValid() point to any problems?

@JWCarlson found the workaround.. (he hit the 5-post limit)

The DESeq2 package will need to be tweaked to account for the latest change in S4Vectors. Creating the class definitions: setClassUnion("characterORNULL", c("character", "NULL”)) setClassUnion(“DataTableORNULL", c(“DataTable", "NULL”)) These were defined in the old S4Vectors but not in the latest version.

That is not the right solution. The slot NAMES comes from SummarizedExperiment; does SummarizedExperiment::SummarizedExperiment() work? Does getClass("SummarizedExperiment") show character_or_NULL ? Are there two versions of SummarizedExperiment installed, maybe tested with

Thanks Martin for helping to dive into this.

I just updated all Bioc packages on my machine and DESeq2 builds and passes CHECK as it does on Bioc servers.

I recognize that my setClassUnion call is a hack. It's a workaround until this gets sorted out and something to convince me that this really is the issue.

In answer to your questions, the constructor works and it shows character_OR_NULL. (As does RangedSummarizedExperiment; DESeqDataSet show NAMES is characterORNULL). And it looks like I have only 1 version installed.

Here is what I get for the NAMES slot of DESeqDataSet today. I don't believe that the version bump in SummarizedExperiment is relevant. 

Can you run biocLite() once again to grab any changes since the release?

The DESeqDataSetFromTximport example is working fine on the Bioc machines and on mine:

https://bioconductor.org/packages/release/bioc/vignettes/tximport/inst/doc/tximport.html#deseq2

Thanks for your work on this Michael.

This is what I upgraded:

I updated all. If I take out my setClassUnion hack, I still see:

It still works with my hack in place.

I'm kind of baffled. It seems like there is an older version of some packages sneaking in, but I don't know how or why.

Yes. It's a strange thing. When I look at showClass("DESeqDataSet"), NAMES is charcterORNULL. But your results show that it is character_OR_NULL.

I agree that from all appearances, my initialization of DESeqDataSet looks like it's pulling in an older version of S4Vectors. I've stepped through the initialization of DESeqDataSet and it looks to me that NAMES in S4Vectors inside the initialization of DESeqDataSet is characterORNULL. But I cannot find where that is done. I'll look some more and see if I can find it.

I had this issue. Turns out I had the new version installed on my machine as the root user but an older version of DESeq2 and BioCinstaller in my ~/R/x86_64-pc-linux-gnu-library/3.4. Manually removed the packages from my users local R library and reran bioClite() then it worked.

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SyntaxError: invalid assignment left-hand side

The JavaScript exception "invalid assignment left-hand side" occurs when there was an unexpected assignment somewhere. It may be triggered when a single = sign was used instead of == or === .

SyntaxError or ReferenceError , depending on the syntax.

What went wrong?

There was an unexpected assignment somewhere. This might be due to a mismatch of an assignment operator and an equality operator , for example. While a single = sign assigns a value to a variable, the == or === operators compare a value.

Typical invalid assignments

In the if statement, you want to use an equality operator ( === ), and for the string concatenation, the plus ( + ) operator is needed.

Assignments producing ReferenceErrors

Invalid assignments don't always produce syntax errors. Sometimes the syntax is almost correct, but at runtime, the left hand side expression evaluates to a value instead of a reference , so the assignment is still invalid. Such errors occur later in execution, when the statement is actually executed.

Function calls, new calls, super() , and this are all values instead of references. If you want to use them on the left hand side, the assignment target needs to be a property of their produced values instead.

Note: In Firefox and Safari, the first example produces a ReferenceError in non-strict mode, and a SyntaxError in strict mode . Chrome throws a runtime ReferenceError for both strict and non-strict modes.

Using optional chaining as assignment target

Optional chaining is not a valid target of assignment.

Instead, you have to first guard the nullish case.

• Assignment operators
• Equality operators
• Web Development

What Is the JavaScript Logical Nullish Assignment Operator?

• Daniyal Hamid
• 24 Dec, 2021

Introduced in ES12, you can use the logical nullish assignment operator ( ??= ) to assign a value to a variable if it hasn't been set already. Consider the following examples, which are all equivalent:

The null coalescing assignment operator only assigns the default value if x is a nullish value (i.e. undefined or null ). For example:

In the following example, x already has a value, therefore, the logical nullish assignment operator would not set a default (i.e. it won't return the value on the right side of the assignment operator):

In case, you use the nullish assignment operator on an undeclared variable, the following ReferenceError is thrown:

This post was published 24 Dec, 2021 by Daniyal Hamid . Daniyal currently works as the Head of Engineering in Germany and has 20+ years of experience in software engineering, design and marketing. Please show your love and support by sharing this post .

HatchJS.com

Cracking the Shell of Mystery

Basic_string _m_construct null not valid: What it is and how to fix it

The C++ standard library provides a number of string classes, including the `std::string` class. `std::string` is a powerful and flexible class that can be used to store and manipulate text data. However, it is important to understand the limitations of `std::string`, especially when it comes to constructing strings from null characters.

In this article, we will discuss the `std::string::_M_construct()` function, which is used to construct a `std::string` object from a null character. We will explain why it is not valid to construct a `std::string` from a null character, and we will show how to avoid this problem.

We will also discuss some of the other ways to construct `std::string` objects, and we will provide some tips for working with null characters in C++.

By the end of this article, you will have a good understanding of the `std::string::_M_construct()` function and how to use it safely. You will also be familiar with the other ways to construct `std::string` objects, and you will be able to avoid problems with null characters in your C++ code.

The basic_string::_m_construct null not valid error is a common error that occurs when an attempt is made to construct a basic_string object with a null pointer as the initial value. This error is caused by a number of different factors, including incorrect assignment statements, null pointer literals, and invalid casts.

In this article, we will discuss the causes of the basic_string::_m_construct null not valid error and how to avoid it. We will also provide some code examples to illustrate how to correctly construct basic_string objects.

What is the basic_string::_m_construct null not valid error?

The basic_string::_m_construct null not valid error occurs when an attempt is made to construct a basic_string object with a null pointer as the initial value. This is invalid because a null pointer cannot be dereferenced, and therefore the basic_string object cannot be initialized.

The error message typically includes the following information:

• The file name where the error occurred
• The line number where the error occurred
• The text of the invalid expression

For example, the following code will cause the basic_string::_m_construct null not valid error:

std::string str = nullptr;

This is because the assignment operator for basic_string objects requires a non-null pointer as its argument.

What causes the basic_string::_m_construct null not valid error?

The most common cause of the basic_string::_m_construct null not valid error is an incorrect assignment statement. For example, the following code will cause the error:

Another common cause of the basic_string::_m_construct null not valid error is an attempt to create a basic_string object with a null pointer literal. For example, the following code will also cause the error:

std::string str = NULL;

This is because the null pointer literal is converted to a null pointer before it is used to initialize the basic_string object.

Finally, the basic_string::_m_construct null not valid error can also be caused by invalid casts. For example, the following code will cause the error:

std::string str = static_cast (nullptr);

This is because the cast from a null pointer to a basic_string pointer is invalid.

How to avoid the basic_string::_m_construct null not valid error

There are a few things you can do to avoid the basic_string::_m_construct null not valid error.

First, make sure that you are using the correct assignment operator for basic_string objects. The assignment operator for basic_string objects requires a non-null pointer as its argument.

Second, avoid using null pointer literals to initialize basic_string objects. Instead, use a non-null pointer or a string literal.

Finally, be careful with casts. Make sure that you are only casting from a valid type to a basic_string pointer.

The basic_string::_m_construct null not valid error is a common error that can be avoided by following a few simple guidelines. By understanding the causes of this error, you can write code that is free from this type of error.

Here are some additional resources that you may find helpful:

• [The C++ Programming Language, 4th Edition](https://www.pearson.com/us/higher-education/product/The-C-Programming-Language-4th-Edition/9780134197783.html)
• [The C++ Standard Library, 3rd Edition](https://www.pearson.com/us/higher-education/product/The-C-Standard-Library-3rd-Edition/9780134043636.html)
• [C++ Reference](https://en.cppreference.com/w/)

The basic_string::_m_construct null not valid error is a compile-time error that occurs when you attempt to construct a basic_string object with a null pointer. This error is caused by the fact that the basic_string class’s constructor requires a non-null pointer to a character array as its first argument. If you attempt to pass a null pointer to the constructor, the compiler will generate an error.

How can I fix the basic_string::_m_construct null not valid error?

To fix this error, you must ensure that the initial value of the basic_string object is not a null pointer. This can be done by either passing a non-null pointer to the constructor, or by initializing the object with a non-null string literal.

Example code

The following code demonstrates how to fix the basic_string::_m_construct null not valid error:

c++ include include

int main() { // Create a basic_string object with a non-null pointer. std::string str = “Hello world”;

// Print the contents of the basic_string object. std::cout

The basic_string::_m_construct null not valid error is a common error that can be easily avoided by ensuring that the initial value of the basic_string object is not a null pointer. By following the steps in this article, you can easily fix this error and continue on with your C++ programming.

Q: What does the error message “basic_string::_M_construct null not valid” mean?

A: This error message means that you are trying to create a C++ string object with a null pointer as the initial value. This is not allowed, as a null pointer cannot be used to store any data.

Q: How can I fix this error?

A: There are a few ways to fix this error. One way is to simply provide a non-null value for the initial value of the string object. For example, you could use the following code:

c++ std::string str(“Hello world”);

Another way to fix this error is to use the C++ `nullptr` keyword. The `nullptr` keyword is a special value that can be used to represent a null pointer. You can use the `nullptr` keyword to initialize a string object as follows:

c++ std::string str(nullptr);

Q: What are the consequences of using a null pointer to initialize a string object?

A: If you use a null pointer to initialize a string object, the string object will be empty. This means that it will not be able to store any data. If you try to access the data in a string object that has been initialized with a null pointer, you will get a compiler error.

Q: Can I use the `std::string::assign()` method to initialize a string object with a null pointer?

A: No, you cannot use the `std::string::assign()` method to initialize a string object with a null pointer. The `std::string::assign()` method takes a C-style string as its argument, and a null pointer is not a valid C-style string.

Q: What other errors can I get when working with C++ strings?

A: There are a number of other errors that you can get when working with C++ strings. Some of the most common errors include:

• Out-of-bounds errors: These errors occur when you try to access a character in a string that is outside of the bounds of the string.
• Invalid character encoding errors: These errors occur when you try to use a character encoding that is not supported by the C++ standard library.
• Memory allocation errors: These errors occur when the C++ standard library cannot allocate enough memory to store a string.

For more information on these errors, please refer to the C++ documentation.

In this article, we discussed the issue of std::basic_string::_M_construct(const char *, size_t) throwing an exception when the input string is null. We presented a possible solution to this problem, which involves using the std::string::npos constant to indicate that the string is null. We also discussed the potential performance implications of this solution, and concluded that it is a viable option for most applications.

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Error in checkSlotAssignment(object, name, value) #44

xuesongjing commented May 22, 2017

JEFworks commented May 22, 2017

Sorry, something went wrong.

mittalan commented Apr 2, 2020 • edited

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This causes a NullPointerException at line 6. So, accessing any field, method, or index of a null object causes a NullPointerException, as can be seen from the examples above. A common way of avoiding the NullPointerException is to check for null: public void doSomething() {. String result = doSomethingElse();

That is not the right solution. The slot NAMES comes from SummarizedExperiment; does SummarizedExperiment::SummarizedExperiment() work? Does getClass("SummarizedExperiment") show character_or_NULL?Are there two versions of SummarizedExperiment installed, maybe tested with

Hi all, I have been stumbling into the same issue for a while now, when documenting packages that include S4 methods named like primitives of the base package. I have a kind of workaround (described further below), but I would like to learn if and what is the proper way of dealing with this kind of situation.

Reference variables at the class or object level will be assigned a null value. Reference variables at the method (stack) level will have an unspecified value (using the C++ term). In practice this is often null, but the standard does not specify what is in the reference variable, only that it must be assigned before use. Using a reference ...

Bitwise XOR assignment (^=) class expression; Comma operator (,) Conditional (ternary) operator; Decrement (--) ... arguments is not valid in fields; SyntaxError: await is only valid in async functions, async generators and modules ... "x" is not a non-null object; TypeError: "x" is read-only; TypeError: can't assign to property "x" on "y": not ...

Note: The parentheses ( ...) around the assignment statement are required when using object literal destructuring assignment without a declaration. { a, b } = { a: 1, b: 2 } is not valid stand-alone syntax, as the { a, b } on the left-hand side is considered a block and not an object literal according to the rules of expression statements.However, ({ a, b } = { a: 1, b: 2 }) is valid, as is ...

Another option is to use the utility class ObjectUtils from the Apache commons-lang3 library. The ObjectUtils's allNull() method has a generic API that handles any type and number of parameters. That method receives an array of Objects and returns true if all values in that array are null.. Otherwise, return false.Let's first add the latest version of the commons-lang3 dependency to our ...

Invalid assignments don't always produce syntax errors. Sometimes the syntax is almost correct, but at runtime, the left hand side expression evaluates to a value instead of a reference, so the assignment is still invalid. Such errors occur later in execution, when the statement is actually executed. js. function foo() { return { a: 1 }; } foo ...

Hi @kevin198930,. You should remove from the matrix/object you provide as input the cells that you removed from the annotation file. inferCNV checks that all the cells in the annotation file are in the matrix, but not the other way around so it could lead to unexpected issues.

In the following example, x already has a value, therefore, the logical nullish assignment operator would not set a default (i.e. it won't return the value on the right side of the assignment operator):

How can I fix the basic_string::_m_construct null not valid error? To fix this error, you must ensure that the initial value of the basic_string object is not a null pointer. This can be done by either passing a non-null pointer to the constructor, or by initializing the object with a non-null string literal. Example code

Seems like the MxAlgebra.R fn algebraErrorChecking (called in mxConstraint) should be catching that the whole rhs is a string?. So this would be a requires to enhance the checking by algebraErrorChecking to include not accepting strings as left or right hand sides.. Currently, can feed algebraErrorChecking this and it doesn't care:

} } // imagine this is setting on an instance and not the type Example.Name = data; // CS8601 - Possible null reference assignment. In the code I have a string type that is never null cause it the property setter converts null assignments to a default value. The compiler doesn't understand this and moans about it though.

Figured this out. Just need to add gene activity to each object PRIOR to integration. I found that it works well to just use Cell Ranger Aggr for the peak calling, but to use each individual sample (not Aggr output) as the input for the Signac integration.

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Error in checkSlotAssignment(object, name, value) #44

xuesongjing commented May 22, 2017

JEFworks commented May 22, 2017

Sorry, something went wrong.

mittalan commented Apr 2, 2020 • edited

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Value of type null is not callable

I got the following error:

When trying to delete an activity,the function is called by:

The $assignment is not null i double checked, but a valid assignment object, i don't know how to solve this issue, please help in this question, thank you in advance

"It sounds like you reused a method name as a variable" - this is true because its definied like:

so it's called like:

this will call finally:

• It doesn't say that $assignment is null, it says $assignment->delete_instance is null. –  Barmar Mar 1 at 20:00
• It sounds like you reused a method name as a variable. Search the code for an assignment to $something->delete_instance . –  Barmar Mar 1 at 20:01
• for me its really strange because the return type of the function is true or false, "It sounds like you reused a method name as a variable" - this is true because its definied like: $modname = 'assign'; $moddelete = $modname .'_delete_instance'; than called like: $moddelete($cm->modinstance); this will call finally: $assignment->delete_instance();//this is where the execution stopped –  Andrewboy Mar 1 at 22:59
• $modname .'_delete_instance' is not $object->delete_instance so I'm not sure that's related. Please post a minimal reproducible example . –  Barmar Mar 1 at 23:02
• The actual code is here: github.com/moodle/moodle/blob/main/mod/assign/lib.php#L51 But I'm not clear which actual line the code is failing on - is it the call to $assignment->delete_instance() or is it a line within the delete_instance() function? –  davosmith Mar 2 at 10:05

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