How to invoke a method of an apex class at run time

Question

We have a usecase where we need to invoke an instance of a class and invoke a method at run time using string. I know with reflection i can instantiate a class. But how do we invoke a method of a class at run time? Could you any share some snippets of code for this please?

Answer 1

You can use an interface to ensure that the invoked class has the required method.

Disclaimer: I mostly hacked this together and haven't run it. Hopefully you get the general idea.

global class InterfaceSample {
    global interface MyInterface {
        void methodToInvoke(string input);
    }

    global class SampleImplementation implements MyInterface  {
        global void methodToInvoke(string input) {
            System.debug(input);
        }
    }
}


public with sharing class TestFactoryClass {

    public static InterfaceSample.MyInterface getInstance(string className) {
        Type t = Type.forName(className);
        if(t == null && className != null) {
            // Attempt to get the type again with the namespace explicitly set to blank
            t = Type.forName('', className);
        }
        if(t == null) {
            System.debug(LoggingLevel.Error, 'Failed to find type for ['+className+']');
            return null;
        }

        // Create an instance to confirm the type
        object testInstance = t.newInstance();
        if(!(testInstance instanceOf InterfaceSample.MyInterface)) {
            return null;
        }

        InterfaceSample.MyInterface interfaceInstance = (InterfaceSample.MyInterface)testInstance;
        return interfaceInstance;
    }
}

Then you can just use the factory class to get an instance of the interface and invoke the methods.

InterfaceSample.MyInterface i = TestFactoryClass.getInstance('InterfaceSample.SampleImplementation');
i.methodToInvoke('Hello World');

Answer 2

No Apex does not support reflection. You could vote for the idea...

I have heard it on the grapevine that there are some major changes being done to the apex compiler, which in theory would mean once they have made these changes they can start adding new features like reflection.

Back to your problem, what is the basic problem you are trying to solve? It is possible you may just need to redesign/rethink your solution?