Builder

定义：将一个复杂对象的构建与它的表示分离，使得同样的构建过程可以创建不同的表示。

通用类图：

示例代码：

// Builder pattern -- Structural example 

using System;
 
using System.Collections.Generic;


namespace DoFactory.GangOfFour.Builder.Structural

{

  /// <summary>

/// MainApp startup class for Structural

/// Builder Design Pattern.

/// </summary>

  public class MainApp

  {
 
    /// <summary>
 
/// Entry point into console application.
 
/// </summary>
 
    public static void Main()
 
    {
 
      // Create director and builders
 
      Director director = new Director();
 
 
 
      Builder b1 = new ConcreteBuilder1();
 
      Builder b2 = new ConcreteBuilder2();
 
 
 
      // Construct two products
 
      director.Construct(b1);
 
      Product p1 = b1.GetResult();
 
      p1.Show();
 
 
 
      director.Construct(b2);
 
      Product p2 = b2.GetResult();
 
      p2.Show();
 
 
 
      // Wait for user
 
      Console.ReadKey();
 
    }
 
  }
 
 
 
  /// <summary>
 
/// The 'Director' class
 
/// </summary>
 
  class Director
 
  {
 
    // Builder uses a complex series of steps
 
    public void Construct(Builder builder)
 
    {
 
      builder.BuildPartA();
 
      builder.BuildPartB();
 
    }
 
  }
 
 
 
  /// <summary>
 
/// The 'Builder' abstract class
 
/// </summary>
 
  abstract class Builder
 
  {
 
    public abstract void BuildPartA();
 
    public abstract void BuildPartB();
 
    public abstract Product GetResult();
 
  }
 
 
 
  /// <summary>
 
/// The 'ConcreteBuilder1' class
 
/// </summary>
 
  class ConcreteBuilder1 : Builder
 
  {
 
    private Product _product = new Product();
 
 
 
    public override void BuildPartA()
 
    {
 
      _product.Add("PartA");
 
    }
 
 
 
    public override void BuildPartB()
 
    {
 
      _product.Add("PartB");
 
    }
 
 
 
    public override Product GetResult()
 
    {
 
      return _product;
 
    }
 
  }
 
 
 
  /// <summary>
 
/// The 'ConcreteBuilder2' class
 
/// </summary>
 
  class ConcreteBuilder2 : Builder
 
  {
 
    private Product _product = new Product();
 
 
 
    public override void BuildPartA()
 
    {
 
      _product.Add("PartX");
 
    }
 
 
 
    public override void BuildPartB()
 
    {
 
      _product.Add("PartY");
 
    }
 
 
 
    public override Product GetResult()
 
    {
 
      return _product;
 
    }
 
  }
 
 
 
  /// <summary>
 
/// The 'Product' class
 
/// </summary>
 
  class Product
 
  {
 
    private List<string> _parts = new List<string>();
 
 
 
    public void Add(string part)
 
    {
 
      _parts.Add(part);
 
    }
 
 
 
    public void Show()
 
    {
 
      Console.WriteLine("\nProduct Parts -------");
 
      foreach (string part in _parts)
 
        Console.WriteLine(part);
 
    }
 
  }
 
}

输出：

Product Parts -------

PartA

PartB
Product Parts -------

PartX

PartY

// Builder pattern -- Real World example 

using System;
 
using System.Collections.Generic;

namespace DoFactory.GangOfFour.Builder.RealWorld

{

  /// <summary>

/// MainApp startup class for Real-World 

/// Builder Design Pattern.

/// </summary>

  public class MainApp

  {

    /// <summary>

/// Entry point into console application.

/// </summary>

    public static void Main()

    {

      VehicleBuilder builder;

      // Create shop with vehicle builders
 
      Shop shop = new Shop();
 
 
 
      // Construct and display vehicles
 
      builder = new ScooterBuilder();
 
      shop.Construct(builder);
 
      builder.Vehicle.Show();
 
 
 
      builder = new CarBuilder();
 
      shop.Construct(builder);
 
      builder.Vehicle.Show();
 
 
 
      builder = new MotorCycleBuilder();
 
      shop.Construct(builder);
 
      builder.Vehicle.Show();
 
 
 
      // Wait for user
 
      Console.ReadKey();
 
    }
 
  }
 
 
 
  /// <summary>
 
/// The 'Director' class
 
/// </summary>
 
  class Shop
 
  {
 
    // Builder uses a complex series of steps
 
    public void Construct(VehicleBuilder vehicleBuilder)
 
    {
 
      vehicleBuilder.BuildFrame();
 
      vehicleBuilder.BuildEngine();
 
      vehicleBuilder.BuildWheels();
 
      vehicleBuilder.BuildDoors();
 
    }
 
  }
 
 
 
  /// <summary>
 
/// The 'Builder' abstract class
 
/// </summary>
 
  abstract class VehicleBuilder
 
  {
 
    protected Vehicle vehicle;
 
 
 
    // Gets vehicle instance
 
    public Vehicle Vehicle
 
    {
 
      get { return vehicle; }
 
    }
 
 
 
    // Abstract build methods
 
    public abstract void BuildFrame();
 
    public abstract void BuildEngine();
 
    public abstract void BuildWheels();
 
    public abstract void BuildDoors();
 
  }
 
 
 
  /// <summary>
 
/// The 'ConcreteBuilder1' class
 
/// </summary>
 
  class MotorCycleBuilder : VehicleBuilder
 
  {
 
    public MotorCycleBuilder()
 
    {
 
      vehicle = new Vehicle("MotorCycle");
 
    }
 
 
 
    public override void BuildFrame()
 
    {
 
      vehicle["frame"] = "MotorCycle Frame";
 
    }
 
 
 
    public override void BuildEngine()
 
    {
 
      vehicle["engine"] = "500 cc";
 
    }
 
 
 
    public override void BuildWheels()
 
    {
 
      vehicle["wheels"] = "2";
 
    }
 
 
 
    public override void BuildDoors()
 
    {
 
      vehicle["doors"] = "0";
 
    }
 
  }
 
 
 
 
 
  /// <summary>
 
/// The 'ConcreteBuilder2' class
 
/// </summary>
 
  class CarBuilder : VehicleBuilder
 
  {
 
    public CarBuilder()
 
    {
 
      vehicle = new Vehicle("Car");
 
    }
 
 
 
    public override void BuildFrame()
 
    {
 
      vehicle["frame"] = "Car Frame";
 
    }
 
 
 
    public override void BuildEngine()
 
    {
 
      vehicle["engine"] = "2500 cc";
 
    }
 
 
 
    public override void BuildWheels()
 
    {
 
      vehicle["wheels"] = "4";
 
    }
 
 
 
    public override void BuildDoors()
 
    {
 
      vehicle["doors"] = "4";
 
    }
 
  }
 
 
 
  /// <summary>
 
/// The 'ConcreteBuilder3' class
 
/// </summary>
 
  class ScooterBuilder : VehicleBuilder
 
  {
 
    public ScooterBuilder()
 
    {
 
      vehicle = new Vehicle("Scooter");
 
    }
 
 
 
    public override void BuildFrame()
 
    {
 
      vehicle["frame"] = "Scooter Frame";
 
    }
 
 
 
    public override void BuildEngine()
 
    {
 
      vehicle["engine"] = "50 cc";
 
    }
 
 
 
    public override void BuildWheels()
 
    {
 
      vehicle["wheels"] = "2";
 
    }
 
 
 
    public override void BuildDoors()
 
    {
 
      vehicle["doors"] = "0";
 
    }
 
  }
 
 
 
  /// <summary>
 
/// The 'Product' class
 
/// </summary>
 
  class Vehicle
 
  {
 
    private string _vehicleType;
 
    private Dictionary<string,string> _parts = 

      new Dictionary<string,string>();
 
 
 
    // Constructor
 
    public Vehicle(string vehicleType)
 
    {
 
      this._vehicleType = vehicleType;
 
    }
 
 
 
    // Indexer
 
    public string this[string key]
 
    {
 
      get { return _parts[key]; }
 
      set { _parts[key] = value; }
 
    }
 
 
 
    public void Show()
 
    {
 
      Console.WriteLine("\n---------------------------");
 
      Console.WriteLine("Vehicle Type: {0}", _vehicleType);
 
      Console.WriteLine(" Frame : {0}", _parts["frame"]);
 
      Console.WriteLine(" Engine : {0}", _parts["engine"]);
 
      Console.WriteLine(" #Wheels: {0}", _parts["wheels"]);
 
      Console.WriteLine(" #Doors : {0}", _parts["doors"]);
 
    }
 
  }
 
}
 

输出：

---------------------------

Vehicle Type: Scooter

Frame   : Scooter Frame

Engine : none

#Wheels: 2

#Doors : 0
---------------------------

Vehicle Type: Car

Frame   : Car Frame

Engine : 2500 cc

#Wheels: 4

#Doors : 4
---------------------------

Vehicle Type: MotorCycle

Frame   : MotorCycle Frame

Engine : 500 cc

#Wheels: 2

#Doors : 0