设计模式：结构型模式：适配器（adapter）



http://www.codeproject.com/Tips/595716/Adapter-Design-Pattern-in-Cplusplus

Using the Code

An adapter pattern converts the interface of a class into another interface the clients expect. Adapter lets classes work together that couldn't otherwise because of incompatible interfaces.

It comprises three components:

• Target: This is the interface with which the client interacts.
• Adaptee: This is the interface the client wants to interact with, but can’t interact without the help of theAdapter.
• Adapter: This is derived from Target and contains the object of Adaptee.

When I shifted from India to London, I took along many of my electrical appliances with me. But there was one problem using them, the pin shape. In India, all the appliances have round pins whereas in London they are flat pinned. Now how do we overcome this problem as I was not ready to buy new plugs. So the adapter came to my rescue (and saved lots of pounds!!!)

I got hold of an adapter plug which has round pins as input and the other end with flat pins (India to UK adapters). This is how I used them with the adapter pattern.

Class description:

• <AbstractPlug>: Abstract Target class
• <Plug>: Concrete Target class
• <AbstractSwitchBoard>: Abstract Adaptee class
• <SwitchBoard>: Concrete Adaptee class
• <Adapter>: Adapter class, our saviour

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// Abstract Targetclass AbstractPlug {public:  void virtual RoundPin(){}  void virtual PinCount(){}};// Concrete Targetclass Plug : public AbstractPlug {public:  void RoundPin() {    cout << " I am Round Pin" << endl;  }  void PinCount() {    cout << " I have two pins" << endl;  }};// Abstract Adapteeclass AbstractSwitchBoard {public:  void virtual FlatPin() {}  void virtual PinCount() {}};// Concrete Adapteeclass SwitchBoard : public AbstractSwitchBoard {public:  void FlatPin() {        cout << " Flat Pin" << endl;  }  void PinCount() {        cout << " I have three pins" << endl;  }};// Adapterclass Adapter : public AbstractPlug {public:  AbstractSwitchBoard *T;  Adapter(AbstractSwitchBoard *TT) {        T = TT;  }  void RoundPin() {        T->FlatPin();  }  void PinCount() {        T->PinCount();  }};// Client codevoid _tmain(int argc, _TCHAR* argv[]){  SwitchBoard *mySwitchBoard = new SwitchBoard; // Adaptee  // Target = Adapter(Adaptee)  AbstractPlug *adapter = new Adapter(mySwitchBoard);  adapter->RoundPin();  adapter->PinCount();}