Apex Method Overloading is not working when called from LWC javascript Controller

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Recently i have observed this weird behaviour and i am not sure is this expected behaviour or i am doing some kind of syntactical error.

I have two method with same name(suppose "methodOfClassA") in a apex class (suppose ClassA). The difference these methods have is number of parameters it accepts.

Now when i am invoking this two methods from lwc javascript controller at two different point of time(let's assume at two button click), only one method is getting invoked which has multiple parameter.

here is how my code looks like:
ApexClass :-

@AuraEnabled
public static string methodOfClassA(string param1){
  return param1;
}
@AuraEnabled
public static string methodOfClassA(string param1,String param2){
  String subString = param1+'-'+param2;
  return subString;
}

Javscript Controller-

invokeSingleParam() {
    methodName({param1:'parameter'})
        .then(resultReturned =>{
            console.log("param1 returned =>",resultReturned);
         })
        .catch(error =>{
            console.log("error ==> ",error.message);
        })
}

invokeSingleMultipleParam(){
    methodName({param1:'One Param',param2:'second Param'})
        .then(resultReturned =>{
            console.log("substring returned =>",resultReturned);
        })
        .catch(error =>{
            console.log("error ==> ",error.message);
        })        
}

here the screenshot of printed console.log

can anyone Please help me, why the polymorphism behavior of apex class is not working here?

Best Answer

This has nothing to do with polymorphism. Polymorphism deals with situations where you have multiple classes that share a common ancestor. What you're dealing with are called "overloaded methods." This is not supported with @AuraEnabled. Each method you want to call must have a unique name. This is because of how the underlying API is designed.

When calling one Apex method from another, the compiler selects the most appropriate overloaded methods based on the method signature (e.g. the count and type of parameters), but the JavaScript API cannot determine which method to use in real-time, so only one is called. If you reversed the order in the source code, you'd probably find that the one-parameter version is called instead, but there is no guarantee. You must use separate names for each version of the method if you want to call them from Aura or LWC.

Note that Aura has an additional restriction that the client-side controller and server-side Apex class cannot have methods by the same name, either, otherwise it is indeterminate which method will be called when using component.get("c.someMethod").

Related Solutions

[SalesForce] Simple Apex class to return a list of strings

You can't instantiate a List like that using an integer. You don't need to explicitly specify how much items are going into the list when it is created. Instead, just remove the integer:

//Instantiate the list
String[] myArray = new List<String>();

You're logic in your loop seems to be incorrect as well. Specifically, myArray's size will always be 0 when you instantiate it. Change your loop logic to:

for(Integer i=0;i<length;i++) {
   // code
}

You want to generate a List of strings based on the i variable. You will want to change your internal logic to:

//Populate the array
myArray.add('Test ' + i);

// Write value to the debug log
System.debug(myArray[i]);

Finally, you want to return that Array. You need to change your method so the return type is no longer void by changing its signature:

public static String[] generateStringArray(Integer length)

then it is just a matter of returning that array at the end of your method:

return myArray;

This would bring it all together as:

public class StringArrayTest {
    //Public Method
    public static String[] generateStringArray(Integer length) {
        //Instantiate the list
        String[] myArray = new List<String>();

        //Iterate throught the list
        for(Integer i=0;i<length;i++) {
            //Populate the array
            myArray.add('Test ' + i);

            // Write value to the debug log
            System.debug(myArray[i]);
        } //end loop

        return myArray;
    }//end method       
}// end class

Some more info on Arrays and Lists, Loops, and Class methods for future reference.

[SalesForce] Cannot Return a List of Strings – Void method must not return a value

You declared your return type as void. Change it to List<String>.

Incorrect

public static void generateStringArray

Correct

public static List<String> generateStringArray

It would be worth your time to read up on Class Methods:

To define a method, specify the following:

Optional: Modifiers, such as public or protected.

Required: The data type of the value returned by the method, such as String or Integer. Use void if the method does not return a value.

Required: A list of input parameters for the method, separated by commas, each preceded by its data type, and enclosed in parentheses (). If there are no parameters, use a set of empty parentheses. A method can only have 32 input parameters.

Required: The body of the method, enclosed in braces {}. All the code for the method, including any local variable declarations, is contained here. Use the following syntax when defining a method:
[public | private | protected | global] [override] [static] data_type method_name 
(input parameters) 
{
// The body of the method
}

It is your data_type that you have incorrectly specified as void in this case.

Best Answer

Related Solutions

[SalesForce] Simple Apex class to return a list of strings

[SalesForce] Cannot Return a List of Strings – Void method must not return a value

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