桥接模式（Bridge）

1.    定义

      将抽象部分与它的实现部分分离，使它们都可以独立变化。

2.      UML 类图

 

3.      结构代码

// Bridge pattern -- Structural example

using System;

 

namespace DoFactory.GangOfFour.Bridge.Structural

{

  ///<summary>

  /// MainApp startup class for Structural

  /// Bridge Design Pattern.

  ///</summary>

  classMainApp

  {

    ///<summary>

    /// Entry point into console application.

    ///</summary>

    staticvoid Main()

    {

      Abstraction ab =new RefinedAbstraction();

 

      // Set implementation and call

      ab.Implementor = new ConcreteImplementorA();

      ab.Operation();

 

      // Change implemention and call

      ab.Implementor = new ConcreteImplementorB();

      ab.Operation();

 

      // Wait for user

      Console.ReadKey();

    }

  }

 

  ///<summary>

  /// The 'Abstraction' class

  ///</summary>

  classAbstraction

  {

    protectedImplementor implementor;

 

    // Property

    publicImplementor Implementor

    {

      set { implementor =value; }

    }

 

    publicvirtual void Operation()

    {

      implementor.Operation();

    }

  }

 

  ///<summary>

  /// The 'Implementor' abstract class

  ///</summary>

  abstractclass Implementor

  {

    publicabstract void Operation();

  }

 

  ///<summary>

  /// The 'RefinedAbstraction' class

  ///</summary>

  classRefinedAbstraction : Abstraction

  {

    publicoverride void Operation()

    {

      implementor.Operation();

    }

  }

 

  ///<summary>

  /// The 'ConcreteImplementorA' class

  ///</summary>

  classConcreteImplementorA : Implementor

  {

    publicoverride void Operation()

    {

      Console.WriteLine("ConcreteImplementorA Operation");

    }

  }

 

  ///<summary>

  /// The 'ConcreteImplementorB' class

  ///</summary>

  classConcreteImplementorB : Implementor

  {

    publicoverride void Operation()

    {

      Console.WriteLine("ConcreteImplementorB Operation");

    }

  }

}

Output

ConcreteImplementorA Operation
ConcreteImplementorB Operation

4.      实例代码

// Bridge pattern -- Real World example

using System;

using System.Collections.Generic;

 

namespace DoFactory.GangOfFour.Bridge.RealWorld

{

  ///<summary>

  /// MainApp startup class for Real-World

  /// Bridge Design Pattern.

  ///</summary>

  classMainApp

  {

    ///<summary>

    /// Entry point into console application.

    ///</summary>

    staticvoid Main()

    {

      // Create RefinedAbstraction

      Customers customers =new Customers("Chicago");

 

      // Set ConcreteImplementor

      customers.Data = new CustomersData();

 

      // Exercise the bridge

      customers.Show();

      customers.Next();

      customers.Show();

      customers.Next();

      customers.Show();

      customers.Add("Henry Velasquez");

 

      customers.ShowAll();

 

      // Wait for user

      Console.ReadKey();

    }

  }

 

  ///<summary>

  /// The 'Abstraction' class

  ///</summary>

  classCustomersBase

  {

    privateDataObject _dataObject;

    protectedstring group;

 

    public CustomersBase(string group)

    {

      this.group = group;

    }

 

    // Property

    publicDataObject Data

    {

      set { _dataObject =value; }

      get {return _dataObject; }

    }

 

    publicvirtual void Next()

    {

      _dataObject.NextRecord();

    }

 

    publicvirtual void Prior()

    {

      _dataObject.PriorRecord();

    }

 

    publicvirtual void Add(string customer)

    {

      _dataObject.AddRecord(customer);

    }

 

    publicvirtual void Delete(string customer)

    {

      _dataObject.DeleteRecord(customer);

    }

 

    publicvirtual void Show()

    {

      _dataObject.ShowRecord();

    }

 

    publicvirtual void ShowAll()

    {

      Console.WriteLine("Customer Group: " + group);

      _dataObject.ShowAllRecords();

    }

  }

 

  ///<summary>

  /// The 'RefinedAbstraction' class

  ///</summary>

  classCustomers : CustomersBase

  {

    // Constructor

    public Customers(string group)

      : base(group)

    {

    }

 

    publicoverride void ShowAll()

    {

      // Add separator lines

      Console.WriteLine();

      Console.WriteLine("------------------------");

      base.ShowAll();

      Console.WriteLine("------------------------");

    }

  }

 

  ///<summary>

  /// The 'Implementor' abstract class

  ///</summary>

  abstractclass DataObject

  {

    publicabstract void NextRecord();

    publicabstract void PriorRecord();

    publicabstract void AddRecord(string name);

    publicabstract void DeleteRecord(string name);

    publicabstract void ShowRecord();

    publicabstract void ShowAllRecords();

  }

 

  ///<summary>

  /// The 'ConcreteImplementor' class

  ///</summary>

  classCustomersData : DataObject

  {

    privateList<string> _customers =new List<string>();

    privateint _current = 0;

 

    public CustomersData()

    {

      // Loaded from a database

      _customers.Add("Jim Jones");

      _customers.Add("Samual Jackson");

      _customers.Add("Allen Good");

      _customers.Add("Ann Stills");

      _customers.Add("Lisa Giolani");

    }

 

    publicoverride void NextRecord()

    {

      if (_current <= _customers.Count - 1)

      {

        _current++;

      }

    }

 

    publicoverride void PriorRecord()

    {

      if (_current > 0)

      {

        _current--;

      }

    }

 

    publicoverride void AddRecord(string customer)

    {

      _customers.Add(customer);

    }

 

    publicoverride void DeleteRecord(string customer)

    {

      _customers.Remove(customer);

    }

 

    publicoverride void ShowRecord()

    {

      Console.WriteLine(_customers[_current]);

    }

 

    publicoverride void ShowAllRecords()

    {

      foreach (string customerin _customers)

      {

        Console.WriteLine(" " + customer);

      }

    }

  }

}

Output

Jim Jones
Samual Jackson
Allen Good

------------------------
Customer Group: Chicago
Jim Jones
Samual Jackson
Allen Good
Ann Stills
Lisa Giolani
Henry Velasquez
------------------------

该文章来自：http://www.dofactory.com/Patterns/PatternBridge.aspx