C#设计模式(15)命令模式（Command Pattern）

命令模式（Command Pattern）

命令模式是一种数据驱动的设计模式，属于行为型模式类别。请求被包装在一个对象中作为命令，并传递给调用对象。调用对象寻找可以处理该命令的合适对象，并将命令传递给相应的对象，该对象执行命令。

实现

1. 步骤 1：创建一个命令接口。

   public interface IOrder {void Execute();
   }

2. 步骤 2：创建一个请求类。

public class Stock {private string name = "ABC";private int quantity = 10;public void Buy(){Console.WriteLine($"Stock [ Name: {name}, Quantity: {quantity} ] bought");}public void Sell(){Console.WriteLine($"Stock [ Name: {name}, Quantity: {quantity} ] sold");}
}

3. 步骤 3：创建实现 IOrder 接口的具体类。

public class BuyStock : IOrder {private Stock abcStock;public BuyStock(Stock abcStock){this.abcStock = abcStock;}public void Execute() {abcStock.Buy();}
}public class SellStock : IOrder {private Stock abcStock;public SellStock(Stock abcStock){this.abcStock = abcStock;}public void Execute() {abcStock.Sell();}
}

4. 步骤 4：创建命令调用类。

public class Broker {private List<IOrder> orderList = new List<IOrder>(); public void TakeOrder(IOrder order){orderList.Add(order);    }public void PlaceOrders(){foreach (IOrder order in orderList) {order.Execute();}orderList.Clear();}
}

5. 步骤 5：使用 Broker 类接受并执行命令。

public class CommandPatternDemo {public static void Main(string[] args) {Stock abcStock = new Stock();BuyStock buyStockOrder = new BuyStock(abcStock);SellStock sellStockOrder = new SellStock(abcStock);Broker broker = new Broker();broker.TakeOrder(buyStockOrder);broker.TakeOrder(sellStockOrder);broker.PlaceOrders();}
}

6. 步骤 6：验证输出。

Stock [ Name: ABC, Quantity: 10 ] bought
Stock [ Name: ABC, Quantity: 10 ] sold