Passing Methods As Parameters: Delegates to the Answer

1 Comment

• This is almost but not quite the same as passing a method as a parameter. A delegate is a method *and an instance* (or a static method with no instance).
  
  
  
  Consider
  
  
  
  class C {
  
  public void Do(int x) { ... }
  
  public void Die(int x) { ... }
  
  }
  
  
  
  and I want to pass the method "Do" like this:
  
  
  
  void Action(C[] ary, magicphrase action)
  
  {
  
  foreach (C c in ary) c.action(3);
  
  }
  
  
  
  A delegate doesn't quite work here because you would bind each object "c" to the action, so that this Action function receives not an array of C[] but rather an array of delegates.
  
  
  
  Action(
  
  new ActionDelegate[] {
  
  new ActionDelegate(ary[0].Do),
  
  new ActionDelegate(ary[1].Do),
  
  new ActionDelegate(ary[2].Do),
  
  new ActionDelegate(ary[3].Do) });
  
  
  
  To be able to pass just the method you need a thunk.
  
  
  
  class C {
  
  static void DoIndirect(C c, int x) {
  
  c.Do(x);
  
  }
  
  }
  
  
  
  Now you can call Action
  
  
  
  Action(ary, new IndirectAction(C.DoIndirect));
  
  
  
  where Action is
  
  
  
  void Action(C[] ary, IndirectAction action)
  
  {
  
  foreach (C c in ary) action(c, 3);
  
  }