Builder Pattern-优快云博客

Builder pattern uses to create a product which contains variant parts. E.g. Vehicles have Frame, Engine, Wheels and doors, Any different vehicles implements its builder functions to create different parts. For bicycles have frame and two wheels and don’t have engine and door.

This real-world code demonstates the Builder pattern in which different vehicles are assembled in a step-by-step fashion. The Shop uses VehicleBuilders to construct a variety of Vehicles in a series of sequential steps.

Hide code

// Builder pattern -- Real World example

using System;
using System.Collections;

namespace DoFactory.GangOfFour.Builder.RealWorld
{
  // MainApp test application

  public class MainApp
  {
    public static void Main ()
    {
      // Create shop with vehicle builders
      Shop shop = new Shop();
      VehicleBuilder b1 = new ScooterBuilder();
      VehicleBuilder b2 = new CarBuilder();
      VehicleBuilder b3 = new MotorCycleBuilder();

      // Construct and display vehicles
      shop.Construct(b1);
      b1.Vehicle.Show();

      shop.Construct(b2);
      b2.Vehicle.Show();

      shop.Construct(b3);
      b3.Vehicle.Show();

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

  // "Director"

  class Shop
  {
    // Builder uses a complex series of steps
    public void Construct(VehicleBuilder vehicleBuilder)
    {
      vehicleBuilder.BuildFrame();
      vehicleBuilder.BuildEngine();
      vehicleBuilder.BuildWheels();
      vehicleBuilder.BuildDoors();
    }
  }

  // "Builder"

  abstract class VehicleBuilder
  {
    protected Vehicle vehicle;

    // Property
    public Vehicle Vehicle
    {
      get{ return vehicle; }
    }

    public abstract void BuildFrame();
    public abstract void BuildEngine();
    public abstract void BuildWheels();
    public abstract void BuildDoors();
  }

  // "ConcreteBuilder1"

  class MotorCycleBuilder : VehicleBuilder
  {
    public override void BuildFrame()
    {
      vehicle = new Vehicle("MotorCycle");
      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";
    }
  }

  // "ConcreteBuilder2"

  class CarBuilder : VehicleBuilder
  {
    public override void BuildFrame()
    {
      vehicle = new Vehicle("Car");
      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";
    }
  }

  // "ConcreteBuilder3"

  class ScooterBuilder : VehicleBuilder
  {
    public override void BuildFrame()
    {
      vehicle = new Vehicle("Scooter");
      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";
    }
  }

  // "Product"

  class Vehicle
  {
    private string type;
    private Hashtable parts = new Hashtable();

    // Constructor
    public Vehicle(string type)
    {
      this.type = type;
    }

    // Indexer (i.e. smart array)
    public object this[string key]
    {
      get{ return parts[key]; }
      set{ parts[key] = value; }
    }

    public void Show()
    {
      Console.WriteLine("/n---------------------------");
      Console.WriteLine("Vehicle Type: {0}", type);
      Console.WriteLine(" Frame : {0}", parts["frame"]);
      Console.WriteLine(" Engine : {0}", parts["engine"]);
      Console.WriteLine(" #Wheels: {0}", parts["wheels"]);
      Console.WriteLine(" #Doors : {0}", parts["doors"]);
    }
  }
}

Output

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