delagation pattern

http://en.wikipedia.org/wiki/Delegation_pattern

Advantage: easy to compose behavior, and easy to change what to be composed.

Disadvantage: harder to understand and inefficient

In software engineering, the delegation pattern is a design pattern in object-oriented programming where an object, instead of performing one of its stated tasks, delegates that task to an associated helper object. There is an Inversion of Responsibility in which a helper object, known as a delegate, is given the responsibility to execute a task for the delegator.

In this Java example, the Printer class has a print method. This print method, rather than performing the print itself, delegates to class RealPrinter. To the outside world it appears that the Printer class is doing the print, but the RealPrinter class is the one actually doing the work.

Delegation is simply passing a duty off to someone/something else. Here is a simple example:

 class RealPrinter { // the "delegate"
     void print() { 
       System.out.println("something"); 
     }
 }

 class Printer { // the "delegator"
     RealPrinter p = new RealPrinter(); // create the delegate 
     void print() { 
       p.print(); // delegation
     } 
 }

 public class Main {
     // to the outside world it looks like Printer actually prints.
     public static void main(String[] args) {
         Printer printer = new Printer();
         printer.print();
     }
 }
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