C# 设计模式系列教程-命令模式

　　　　5.3.2 系统需要将请求者和接收者解耦，使得调用者和接收者不直接交互。

　　　　5.3.3 系统需要在不同时间指定请求、请求排队和执行请求。

　　　　5.3.4 系统需要将一组操作组合在一起，即支持宏命令。

6. 应用举例：银行帐号的存款、提款

　　6.1 类图

　　6.2 代码实现

 /// <summary>
 /// 银行帐号
 /// </summary>
 public class Account
 {
  /// <summary>
  /// 帐号总金额
  /// </summary>
  private decimal totalAmount { get; set; }

  /// <summary>
  /// 存钱
  /// </summary>
  /// <param name="amount"></param>
  public void MoneyIn(decimal amount)
  {
   this.totalAmount += amount;
  }

  /// <summary>
  /// 取钱
  /// </summary>
  /// <param name="amount"></param>
  public void MoneyOut(decimal amount)
  {
   this.totalAmount -= amount;
  }

  public decimal GetTotalAmout()
  {
   return totalAmount;
  }
 }

 public abstract class Command
 {
  protected Account account;

  public Command(Account account)
  {
   this.account = account;
  }

  public abstract void Execute();
 }

 /// <summary>
 /// 存款命令
 /// </summary>
 public class MoneyInCommand : Command
 {
  private decimal amount;

  public MoneyInCommand(Account account, decimal amount)
   : base(account)
  {
   this.amount = amount;
  }

  /// <summary>
  /// 实现存钱命令
  /// </summary>
  public override void Execute()
  {
   account.MoneyIn(amount);
  }
 }

 /// <summary>
 /// 取款命令类
 /// </summary>
 public class MoneyOutCommand : Command
 {
  private decimal amount;
  public MoneyOutCommand(Account account, decimal amount)
   : base(account)
  {
   this.amount = amount;
  }

  /// <summary>
  /// 实现取钱命令
  /// </summary>
  public override void Execute()
  {
   account.MoneyOut(amount);
  }
 }

 public class Invoker
 {
  private Command command;

  public void SetCommand(Command command)
  {
   this.command = command;
  }

  public void ExecuteCommand()
  {
   command.Execute();
  }
 }

 class Program
 {
  static void Main(string[] args)
  {
   // 创建银行帐号
   Account account = new Account();
   // 创建一个存入500元的命令
   Command commandIn = new MoneyInCommand(account,500);
   // 创建一个调度者
   BankAccount.Invoker invoker = new BankAccount.Invoker();

   // 设置存钱命令
   invoker.SetCommand(commandIn);
   // 执行
   invoker.ExecuteCommand();
   Console.WriteLine("The current amount is " + account.GetTotalAmout().ToString("N2"));

   // 再次存入500
   Command commandIn2 = new MoneyInCommand(account, 500);
   invoker.SetCommand(commandIn2);
   invoker.ExecuteCommand();
   Console.WriteLine("The current amount is " + account.GetTotalAmout().ToString("N2"));

   // 取出300
   Command commandOut = new MoneyOutCommand(account, 300);
   invoker.SetCommand(commandOut);
   invoker.ExecuteCommand();
   Console.WriteLine("The current amount is " + account.GetTotalAmout().ToString("N2"));

   Console.Read();
  }
 }

								 
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