Delegates: Example in C#
When would you need a delegate?
When you want to delegate responsibility for some piece of work elsewhere without creating a compile time dependency.
If you find yourself in a situation where you feel like the argument to a method should be another method, a delegate may be appropriate.
When you want to delegate responsibility for some piece of work elsewhere without creating a compile time dependency.
If you find yourself in a situation where you feel like the argument to a method should be another method, a delegate may be appropriate.
using System;
//Similar to a function prototype
public delegate void DoStuffDelegate(string s);
public class Test{
public static void Main(string[] args){
SomeOtherClass someOtherClass = new SomeOtherClass();
//Call the DoSomething method on our object instance, passing it various
//pointers to functions -- any will do as long as they match the delegate
//function prototype
someOtherClass.DoSomething(new DoStuffDelegate(PrintUpper));
someOtherClass.DoSomething(new DoStuffDelegate(PrintLower));
//note that you can delegate anything! -- here's a delegation to a static method
someOtherClass.DoSomething(new DoStuffDelegate(SomeThirdClass.PrintReverse));
}
public static void PrintUpper(string s){
Console.WriteLine(s.ToUpper());
}
public static void PrintLower(string s){
Console.WriteLine(s.ToLower());
}
}
public class SomeOtherClass{
//This method knows about the function prototype of DoStuffDelegate(string),
//but it doesn't know at compile time what it's going to get
public void DoSomething(DoStuffDelegate doStuffDelegate){
doStuffDelegate("This is like a blind date -- I don't know who I'm going to get!");
}
}
public static class SomeThirdClass{
public static void PrintReverse(string s){
for(int i = s.Length-1; i >= 0; --i)
Console.Write(s[i]);
}
}
Output:
jknight@shadowbox:/tmp$ mono Delegate.exe THIS IS LIKE A BLIND DATE -- I DON'T KNOW WHO I'M GOING TO GET! this is like a blind date -- i don't know who i'm going to get! !teg ot gniog m'I ohw wonk t'nod I -- etad dnilb a ekil si sihT jknight@shadowbox:/tmp$