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 orderList = new List(); 
  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