Language support for the decorator design pattern #124
Description
Not sure if this one is worthy here, or even it this one could be useful. I mostly use decorators in favor of aggregation rather than inheritance. And there are situations when most of the methods, implemented from the interface, are simply delegated methods. Such methods can be easily generated with a compiler. This is more significant when the implemented interface is heavy and has a bunch of methods. It would be nice if it's allowed to implement necessary methods only, and let the compiler generate the rest of them. Let's say:
public interface IFoo {
int Do1();
int Do2();
int Do3();
int Do4();
int Do5();
int Do6();
int Do7();
}
// +--- whatever nice thingy to denote a decorator
// V decoratee must be an instance of IFoo
public sealed class Bar : IFoo for decoratee {
// if we need a private constructor
private Bar(IFoo decoratee) {
this.decoratee = decoratee;
}
// ... and a factory method
public static IFoo Bar(IFoo decoratee) {
return new Bar(decoratee);
}
// then just decorate what's needed
public int Do4() {
Console.WriteLine("Do4() is decorated");
return decoratee.Do4();
}
// the rest, Do1--Do3 and Do5--Do7 are automatically generated
}
UPDATE Feb 3, 2016
Kotlin supports the same feature with slightly different syntax: https://kotlinlang.org/docs/reference/delegation.html