Adapter-优快云博客

在 Adapter模式的两种模式中，有一个很重要的概念就是接口继承和实现继承的区别和

联系。接口继承和实现继承是面向对象领域的两个重要的概念，接口继承指的是通过继承，

子类获得了父类的接口，而实现继承指的是通过继承子类获得了父类的实现（并不统共接

口）。在 C++中的 public继承既是接口继承又是实现继承，因为子类在继承了父类后既可以

对外提供父类中的接口操作，又可以获得父类的接口实现。当然我们可以通过一定的方式和

技术模拟单独的接口继承和实现继承，例如我们可以通过 private 继承获得实现继承的效果

（private 继承后，父类中的接口都变为 private，当然只能是实现继承了。），通过纯抽象基

类模拟接口继承的效果，但是在 C++中 pure virtual function 也可以提供默认实现，因此这是

不纯正的接口继承，但是在 Java 中我们可以 interface 来获得真正的接口继承了。

This real-world code demonstrates the use of a legacy chemical databank. Chemical compound objects access the databank through an Adapter interface.

participants

The classes and/or objects participating in this pattern are:

Target (ChemicalCompound)
- defines the domain-specific interface that Client uses.
Adapter (Compound)
- adapts the interface Adaptee to the Target interface.
Adaptee (ChemicalDatabank)
- defines an existing interface that needs adapting.
Client (AdapterApp)
- collaborates with objects conforming to the Target interface.

// Adapter pattern -- Real World example

using System;

namespace DoFactory.GangOfFour.Adapter.RealWorld
{

  // MainApp test application

  class MainApp
  {
    static void Main()
    {
      // Non-adapted chemical compound
      Compound stuff = new Compound("Unknown");
      stuff.Display();

      // Adapted chemical compounds
      Compound water = new RichCompound("Water");
      water.Display();

      Compound benzene = new RichCompound("Benzene");
      benzene.Display();

      Compound alcohol = new RichCompound("Alcohol");
      alcohol.Display();

      // Wait for user
      Console.Read();
    }
  }

  // "Target"

  class Compound
  {
    protected string name;
    protected float boilingPoint;
    protected float meltingPoint;
    protected double molecularWeight;
    protected string molecularFormula;

    // Constructor
    public Compound(string name)
    {
      this.name = name;
    }

    public virtual void Display()
    {
      Console.WriteLine("/nCompound: {0} ------ ", name);
    }
  }

  // "Adapter"

  class RichCompound : Compound
  {
    private ChemicalDatabank bank;

    // Constructor
    public RichCompound(string name) : base(name)
    {
    }

    public override void Display()
    {
      // Adaptee
      bank = new ChemicalDatabank();
      boilingPoint = bank.GetCriticalPoint(name, "B");
      meltingPoint = bank.GetCriticalPoint(name, "M");
      molecularWeight = bank.GetMolecularWeight(name);
      molecularFormula = bank.GetMolecularStructure(name);

      base.Display();
      Console.WriteLine(" Formula: {0}", molecularFormula);
      Console.WriteLine(" Weight : {0}", molecularWeight);
      Console.WriteLine(" Melting Pt: {0}", meltingPoint);
      Console.WriteLine(" Boiling Pt: {0}", boilingPoint);
    }
  }

  // "Adaptee"

  class ChemicalDatabank
  {
    // The Databank 'legacy API'
    public float GetCriticalPoint(string compound, string point)
    {
      float temperature = 0.0F;

      // Melting Point
      if (point == "M")
      {
        switch (compound.ToLower())
        {
          case "water" : temperature = 0.0F; break;
          case "benzene" : temperature = 5.5F; break;
          case "alcohol" : temperature = -114.1F; break;
        }
      }
      // Boiling Point
      else
      {
        switch (compound.ToLower())
        {
          case "water" : temperature = 100.0F; break;
          case "benzene" : temperature = 80.1F; break;
          case "alcohol" : temperature = 78.3F; break;
        }
      }
      return temperature;
    }

    public string GetMolecularStructure(string compound)
    {
      string structure = "";

      switch (compound.ToLower())
      {
        case "water" : structure = "H20"; break;
        case "benzene" : structure = "C6H6"; break;
        case "alcohol" : structure = "C2H6O2"; break;
      }
      return structure;
    }

    public double GetMolecularWeight(string compound)
    {
      double weight = 0.0;
      switch (compound.ToLower())
      {
        case "water" : weight = 18.015; break;
        case "benzene" : weight = 78.1134; break;
        case "alcohol" : weight = 46.0688; break;
      }
      return weight;
    }
  }
}

Output

Compound: Unknown ------

Compound: Water ------
Formula: H20
Weight : 18.015
Melting Pt: 0
Boiling Pt: 100

Compound: Benzene ------
Formula: C6H6
Weight : 78.1134
Melting Pt: 5.5
Boiling Pt: 80.1

Compound: Alcohol ------
Formula: C2H6O2
Weight : 46.0688
Melting Pt: -114.1
Boiling Pt: 78.3