Bridge Design Pattern

The Bridge pattern is designed to separate a class's interface from its implementation so you can vary or replace the implementation without changing the client code (see the Bridge pattern Wikipedia entry).

Lets see what that means in a simpler way.

In following example polymorphism is used inorder to give Person Class different implementations.

	class Person{
	public:
	Person(){}
	virtual void introduce() = 0;
	};
	class John : public Person{
	public:
	John(){}
	void introduce(){
	//print I'm John
	}
	};
	class Ann : public Person{
	public:
	Ann(){}
	void introduce(){
	//print I'm Ann
	}
	};

view raw BridgeDP_1.cpp hosted with ❤ by GitHub

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There are lot of people by same name. Say we want to introduce a new property home town.
If we follow this pattern code would be as follows.

	class Person{
	public:
	Person(){}
	virtual void introduce() = 0;
	};
	class John1 : public Person{
	public:
	John(){}
	void introduce(){
	//print I'm John and I'm from Newyork
	}
	};
	class John2 : public Person{
	public:
	John(){}
	void introduce(){
	//print I'm John and I'm from Los angeles
	}
	};
	class Ann1 : public Person{
	public:
	Ann(){}
	void introduce(){
	//print I'm Ann and I'm from Newyork
	}
	};
	class Ann2 : public Person{
	public:
	Ann(){}
	void introduce(){
	//print I'm Ann and I'm from Los angeles
	}
	};

view raw BridgeDP_2.cpp hosted with ❤ by GitHub

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That is code is hard to maintain and reusability is low. We can use Bridge design pattern to improve that code by seperating implementation of home town.

---

	class Person{
	public:
	Person(){}
	virtual void introduce(Town t) = 0;
	};
	class Town{
	public:
	Town(){}
	virtual void name() = 0;
	};
	class Newyork : public Town {
	void name(){
	//print NewYork
	}
	};
	class LA : public Town {
	void name(){
	//print Los angeles
	}
	};
	class John1 : public Person{
	public:
	John(){}
	void introduce(Town t){
	//print I'm John and I'm from
	t.name();
	}
	};
	class Ann1 : public Person{
	public:
	Ann(){}
	void introduce(Town t){
	//print I'm Ann and I'm from
	t.name();
	}
	};

view raw BridgeDP_3.cpp hosted with ❤ by GitHub

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