【C#设计模式(15)——命令模式(Command Pattern)】

前言

命令模式的关键通过将请求封装成一个对象，使命令的发送者和接收者解耦。这种方式能更方便地添加新的命令，如执行命令的排队、延迟、撤销和重做等操作。

代码

#region 基础的命令模式
//命令（抽象类）
public abstract class Command
{public abstract void Execute();
}
//发送命令
public class SendCommand : Command
{private Receiver receiver;public SendCommand(Receiver receiver){this.receiver = receiver;}public override void Execute(){receiver.Execute();}
}
//接收命令
public class Receiver
{public void Execute(){Console.WriteLine("receiver execute the command...");}
}
//调用者命令
public class Invoker
{private Command command;public void SetCommand(Command command){this.command = command;}public void ExecuteCommand(){command.Execute();}
}
#endregion#region 添加新的命令模式
//新命令
public class NewCommand : Command
{private NewReceiver newReceiver;public NewCommand(NewReceiver newReceiver){this.newReceiver = newReceiver;}public override void Execute(){newReceiver.Execute();}
}
//使用新接收者
public class NewReceiver
{public void Execute(){Console.WriteLine("new reveiver execute the newCommand...");}
}#endregion#region 命令的请求的排队和延迟执行
//命令执行者
public class CommandInvoker
{private List<Command> commandQueue = new List<Command>();public void AddCommand(Command command){commandQueue.Add(command);}public void ExecuteCommands(){foreach (Command command in commandQueue){command.Execute();}commandQueue.Clear();}public void DelayExecute(Command command,int delay){Console.WriteLine($"等待开始....时间：{delay}ms");new Thread(() =>{Console.WriteLine($"延时执行开始==>");Thread.Sleep(delay);command.Execute();Console.WriteLine($"finish time:{Environment.NewLine}{DateTime.Now.ToString("HH:mm:ss fff")}");Console.WriteLine($"==>延时执行完毕...");}).Start();}
}
#endregion#region 命令撤销和重做操作
public interface ICommand
{void Execute();void Undo(); 
}public class HistoryCommand : ICommand
{private HistoryReceiver historyReceiver;public HistoryCommand(HistoryReceiver historyReceiver){this.historyReceiver = historyReceiver;}public void Execute(){historyReceiver.Execute();}public void Undo(){historyReceiver.UndoExecute();}
}public class HistoryReceiver
{public void Execute(){Console.WriteLine("history receiver executes the command...");}public void UndoExecute(){Console.WriteLine("history receiver undoes the command...");}
}
public class HistoryInvoker
{private Stack<ICommand> commandStack = new Stack<ICommand>();public void ExecuteCommand(ICommand command){command.Execute();commandStack.Push(command);}public void Undo(){if (commandStack.Count > 0){ICommand command = commandStack.Pop();Console.WriteLine("command Undo");command.Undo();}else{Console.WriteLine("No commands to undo.");}}public void Redo(){if (commandStack.Count>0){ICommand command = commandStack.Peek();Console.WriteLine("command Redo");command.Execute();}else{Console.WriteLine("No commands to redo.");}}
}/** 行为型模式：Behavioral Pattern* 命令模型：Command Pattern*/internal class Program{static void Main(string[] args){//命令模式：简单实现Receiver receiver = new Receiver();Command sendCommand = new SendCommand(receiver);Invoker invoker = new Invoker();invoker.SetCommand(sendCommand);invoker.ExecuteCommand();Console.WriteLine("添加新命令------------------------------------");// 命令模式：添加新命令NewReceiver newReceiver = new NewReceiver();Command newCommand = new NewCommand(newReceiver);invoker.SetCommand(newCommand);invoker.ExecuteCommand();Console.WriteLine("请求队列------------------------------------");//命令模式：请求队列Receiver receiver1 = new Receiver();Command command1 = new SendCommand(receiver1);Command command2 = new SendCommand(receiver1);CommandInvoker commandInvoker = new CommandInvoker();commandInvoker.AddCommand(command1);commandInvoker.AddCommand(command2);commandInvoker.ExecuteCommands();Console.WriteLine("延时执行------------------------------------");Console.WriteLine($"{DateTime.Now.ToString("HH:mm:ss fff")}");//命令模式：延时执行commandInvoker.DelayExecute(command1,1000);Console.WriteLine("准备撤销重做------------------------------------");HistoryReceiver historyReceiver = new HistoryReceiver();ICommand command3 = new HistoryCommand(historyReceiver);ICommand command4 = new HistoryCommand(historyReceiver);HistoryInvoker historyInvoker = new HistoryInvoker();historyInvoker.ExecuteCommand(command3);historyInvoker.ExecuteCommand(command4);Console.WriteLine("执行撤销重做------------------------------------");//撤销最后一个命令historyInvoker.Undo();historyInvoker.Undo();//重做最后一个撤销命令historyInvoker.Redo();Console.WriteLine("END------------------------------------");Console.ReadLine();}}
#endregion

运行结果