《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).