《模式——工程化实现及扩展》（设计模式C# 版）《创建者模式 Builder》——正文完整示例

转自：《模式——工程化实现及扩展》（设计模式C# 版）

http://www.cnblogs.com/callwangxiang/

 

 

本章正文通过Attribute指导Builder构造过程的完整示例

 

 

1、采用BuildStep定义装配过程的测试类型

 

    #region 采用BuildStep定义装配过程的测试类型

    /// <summary>
    /// 用于显示测试结果的委托
    /// </summary>
    /// <remarks>
    ///     Action<string>是实际处理Build Step操作内容的委托
    /// </remarks>
    static Action<string, Action<string>> buildStepHandler = (x, y) =>
    {
        Trace.WriteLine("add " + x);
        y(x);
    };

    class Car
    {
        public IList<string> Parts { get; private set; }
        public Car(){Parts = new List<string>();}

        /// <summary>
        /// 为汽车添加轮胎
        /// </summary>
        /// <remarks>
        ///     Attributed Builder第二个执行的Setp
        ///     执行4次，即为每辆汽车装配增加4个轮胎
        /// </remarks>
        [BuildStep(2, 4)]
        public void AddWheel() { buildStepHandler("wheel", Parts.Add); }

        /// <summary>
        /// 为汽车装配引擎
        /// </summary>
        /// <remarks>
        ///     没有通过Attribute标注的内容，因此不会被Attributed Builder执行
        /// </remarks>
        public void AddEngine() { buildStepHandler("engine", Parts.Add); }

        /// <summary>
        /// 为汽车装配车身
        /// </summary>
        /// <remarks>
        ///     Attributed Builder第一个执行的Setp
        ///     执行1次，即为每辆汽车装配增加1个车身
        /// </remarks>
        [BuildStep(1)]
        public void AddBody() { buildStepHandler("body", Parts.Add); }
    }

    class Computer
    {
        public string Bus { get; private set; }
        public string Monitor { get; private set; }
        public string Disk { get; private set; }
        public string Memory { get; private set; }
        public string Keyboard { get; private set; }
        public string Mouse { get; private set; }

        /// <summary>
        /// 缓存Computer类型的所有Property
        /// </summary>
        static PropertyInfo[] properties = typeof (Computer).GetProperties();

        /// <summary>
        /// 获得Computer类型指定名称Property的Setter方法委托
        /// </summary>
        /// <param name="target">Computer类型实例</param>
        /// <param name="name">Property名称</param>
        /// <returns>指定名称Property的Setter方法委托</returns>
        static Action<string> GetSetter(Computer target, string name)
        {
            var property = properties.Where(x => string.Equals(x.Name, name)).FirstOrDefault();
            return x => property.SetValue(target, x, null);
        }

        [BuildStep(1)]
        public void LayoutBus()
        {
            buildStepHandler("bus", GetSetter(this, "Bus"));
        }

        [BuildStep(2)]
        public void AddDiskAndMemory()
        {
            buildStepHandler("disk", GetSetter(this, "Disk"));
            buildStepHandler("16G memory", GetSetter(this, "Memory"));
        }

        [BuildStep(3)]
        public void AddUserInputDevice()
        {
            buildStepHandler("USB mouse", GetSetter(this, "Mouse"));
            buildStepHandler("keyboard", GetSetter(this, "Keyboard"));
        }

        [BuildStep(4)]
        public void ConnectMonitor()
        {
            buildStepHandler("monitor", GetSetter(this, "Monitor"));
        }
    }

    #endregion

 

 

 2、执行单元测试

[TestMethod]
public void BuildComputerByAttributeDirection()
{
    Trace.WriteLine("\nassembly computer");
    var computer = new Computer();
    Assert.IsNull(computer.Keyboard);
    Assert.IsNull(computer.Memory);
    computer = new Builder<Computer>().BuildUp();
    Assert.IsNotNull(computer.Bus);
    Assert.IsNotNull(computer.Monitor);
    Assert.IsNotNull(computer.Disk);
    Assert.IsNotNull(computer.Memory);
    Assert.IsNotNull(computer.Keyboard);
    Assert.IsNotNull(computer.Mouse);
}

[TestMethod]
public void BuildCarByAttributeDirection()
{
    Trace.WriteLine("build car");
    var car = new Builder<Car>().BuildUp();
    Assert.IsNotNull(car);
    Assert.IsFalse(car.Parts.Contains("engine")); // 不会被执行的内容
    Assert.AreEqual<string>("body", car.Parts.ElementAt(0));
    for (var i = 1; i <= 4; i++)
        Assert.AreEqual<string>("wheel", car.Parts.ElementAt(i));
}

 

 3、Output窗口输出内容

------ Test started: Assembly: Builder.Tests.dll ------


assembly computer
add bus
add disk
add 16G memory
add USB mouse
add keyboard
add monitor

build car
add body
add wheel
add wheel
add wheel
add wheel

2 passed, 0 failed, 0 skipped, took 0.70 seconds (MSTest 10.0).