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My Favourite Design Patterns - Adapter

Problem: I have a class that almost does what I need- but I don’t like the access methods.


Solution: Create a wrapper (adapter) around an existing class that you don’t control. The wrapper makes the object conform to your needs.


Example:


The Integer class in Java.

This class wraps itself around the “int” data type.


Example:



In this example, we want to create a Circle object. But there exists an object called XX-Circle, which has the required functionality of Circle.

The idea is to create Circle object as a wrapper for XX-Circle hence reusing the functionality of XX-Circle.


Pros


  • Only 1 new object, no additional indirection
  • Less code required than the object Adapter
  • Can override Adaptee's behaviour as required
  • Doesn't require sub-classing to work


Cons


  • Some time harder to override Adaptee behaviour
  • Requires more code to implement properly




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