D365FO: Inheritance + Extensions + RealTime

[wojzeh]

Wrapping a base method in an extension of a derived class
The following example shows how to wrap a base method in an extension of a derived class. For this example, the following class hierarchy is used.

class A
{
    public void salute(str message)
    {   
        info(message);
    }
}

class B extends A {}
class C extends A {}

Therefore, there is one base class, A. Two classes, B and C, are derived from A. We will augment or create an extension class of one of the derived classes (in this case, B), as shown here.

[ExtensionOf(classStr(B))]
final class B_Extension
{
    public void salute(str message)
    {
        next salute(message);
        info("B extension");
    }
}

Although the B_Extension class is an extension of B, and B doesn't have a method definition for the salute method, you can wrap the salute method that is defined in the base class, A. Therefore, only instances of the B class will include the wrapping of the salute method. Instances of the A and C classes will never call the wrapper method that is defined in the extension of the B class.

This behavior becomes clearer if we implement a method that uses these three classes.

class ProgramTest 
{
    public static void main(Args args)
    {
        var a = new A();
        var b = new B();
        var c = new C();

        a.salute("Hi");
        b.salute("Hi");
        c.salute("Hi");
    }
}

For calls to a.salute(“Hi”) and c.salute(“Hi”), the Infolog shows only the message “Hi.” However, when b.salute(“Hi”) is called, the Infolog shows “Hi” followed by “B extension.”

By using this mechanism, you can wrap the original method only for specific derived classes.

https://docs.microsoft.com/en-us/dyn...d-wrapping-coc