Professional .NET 2.0 Generics

13.9. Calling Generic Delegates

Generic delegates cannot be defined within J#. However, in sticking with our "consumer-only" theme, they are allowed to be constructed and used with J#. To illustrate this point, you must first define a delegate in one of the generic-producer languages (C# for this example). Its declaration appears as follows:

[C# code]
public delegate void SampleDelegate<T, U>(T val1, U val2);

With this delegate defined, you can then import and use it freely throughout your J# solutions. The following example represents an example of this delegate being employed with J#:

[J# code]
public class TestGenericDelegates {
    public TestGenericDelegates() { }

    public void ProcessItems(SampleDelegate<String, double> aDelegate) {
        aDelegate.Invoke("Param1", 929.00);
    }

    public void Processor(String val1, double val2) {
        System.out.println(val1);
        System.out.println(val2);
    }

    public void CallMethodWithDelegate() {
        SampleDelegate<String, double> myDelegate =
                                 new SampleDelegate<String, double>(Processor);
        ProcessItems(myDelegate);
    }
}

You'll notice the ProcessItems() method here references the SampleDelegate<T, U> as the type for its parameter. The Processor() method is then declared with a signature that matches that of the declared delegate, allowing it to be successfully instantiated and passed as a parameter in the CallMethodWithDelegate() method.