class1.cs

《深入浅出设计模式》的完整源代码

using System;
using System.Collections;
//抽象命令类
abstract class Command
{
	abstract public void Execute();
	abstract public void UnExecute();
}
//具体命令类
class CalculatorCommand : Command
{
	private char @operator;
	int operand;
	Calculator calculator;
	public CalculatorCommand( Calculator calculator,
		char @operator, int operand )
	{
		this.calculator = calculator;
		this.@operator = @operator;
		this.operand = operand;
	}
	public char Operator
	{
		set{ @operator = value; }
	}

	public int Operand
	{
		set{ operand = value; }
	}
	override public void Execute()
	{
		calculator.Operation( @operator, operand );
	}
 
	override public void UnExecute()
	{
		calculator.Operation( Undo( @operator ), operand );
	}
	private char Undo( char @operator )
	{
		char undo = ' ';
		switch( @operator )
		{
			case '+': undo = '-'; break;
			case '-': undo = '+'; break;
			case '*': undo = '/'; break;
			case '/': undo = '*'; break;
		}
		return undo;
	}
}
//接收者
class Calculator
{
	private int total = 0;
	public void Operation( char @operator, int operand )
	{
		switch( @operator )
		{
			case '+': total += operand; break;
			case '-': total -= operand; break;
			case '*': total *= operand; break;
			case '/': total /= operand; break;
		}
		Console.WriteLine( "Total = {0} (following {1} {2})",
			total, @operator, operand );
	}
}
//调用者
class User
{
	private Calculator calculator = new Calculator();
	private ArrayList commands = new ArrayList();
	private int current = 0;
	public void Redo( int levels )
	{
		Console.WriteLine( "---- Redo {0} levels ", levels );
		// 执行重做操作
		for( int i = 0; i < levels; i++ )
			if( current < commands.Count - 1 )
				((Command)commands[ current++ ]).Execute();
	}

	public void Undo( int levels )
	{
		Console.WriteLine( "---- Undo {0} levels ", levels );
		// 执行取消操作
		for( int i = 0; i < levels; i++ )
			if( current > 0 )
				((Command)commands[ --current ]).UnExecute();
	}

	public void Compute( char @operator, int operand )
	{
		//生成命令并且执行它
		Command command = new CalculatorCommand(
			calculator, @operator, operand );
		command.Execute();

		//在取消列中增加这个命令
		commands.Add( command );
		current++;
	}
}

/// <summary>
///命令应用测验
/// </summary>
public class CommandApp
{
	public static void Main( string[] args )
	{
		//生成用户，让它来计算
		User user = new User();

		user.Compute( '+', 100 );
		user.Compute( '-', 50 );
		user.Compute( '*', 10 );
		user.Compute( '/', 2 );
		// 取消，重做一些命令
		user.Undo( 4 );
		user.Redo( 3 );
		Console.Read();
	}
}