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单例模式与装饰器结合

design-patterns c#

Mike · 技术社区 · 16 年前

附件是一个经典的装饰图案。我的问题是你如何修改下面的代码,这样你就可以在披萨上包上每一个馅饼的0或1个馅饼

现在,我可以吃一个比萨饼类的pepporini->香肠->pepporini->比萨饼,总成本高达10美元,pepporini要两次收费。

我不想使用责任链模式,因为顺序无关紧要,不是所有的配料都用上了?

谢谢你

namespace PizzaDecorator
{
public interface IPizza
{
    double CalculateCost();
}

public class Pizza: IPizza
{
    public Pizza()
    {
    }

    public double CalculateCost()
    {
        return 8.00;
    }

}

public abstract class Topping : IPizza
{
    protected IPizza _pizzaItem;

    public Topping(IPizza pizzaItem)
    {
        this._pizzaItem = pizzaItem;
    }

    public abstract double CalculateCost();

}

public class Pepporini : Topping
{
    public Pepporini(IPizza pizzaItem)
        : base(pizzaItem) 
    {   
    }

    public override  double CalculateCost()
    {
        return this._pizzaItem.CalculateCost() + 0.50;
    }


}

public class Sausage : Topping
{
    public Sausage(IPizza pizzaItem)
        : base(pizzaItem)
    {
    }


    public override double CalculateCost()
    {
        return this._pizzaItem.CalculateCost() + 1.00;
    }
}

public class Onions : Topping
{
    public Onions(IPizza pizzaItem)
        : base(pizzaItem)
    {
    }

    public override double CalculateCost()
    {
        return this._pizzaItem.CalculateCost() + .25;
    }  
}
}

2 回复 | 直到 16 年前

James 16 年前

我会创造一个 Topping 有价格的班级 Pizza 类支持多个浇头。然后根据每一个加在上面的东西来计算价格。

public interface IPizza
{
    double CalculateCost();
}

public class Pizza : IPizza
{
    private List<Topping> toppings = new List<Topping>();
    private double stdCost;

    public Pizza(double cost)
    {
        // this would be the standard cost of the pizza (before any toppings have been added)
        stdCost = cost;
    }

    public Pizza(IList<Topping> toppings)
    {
        this.toppings.AddRange(toppings);
    }

    public void AddTopping(Topping topping)
    {
        this.toppings.Add(topping);
    }

    public void RemoveTopping(Topping topping)
    {
        this.toppings.Remove(topping);
    }

    public double CalculateCost()
    {
        var total = stdCost;
        foreach (var t in toppings)
        {
            total += t.Price;
        }
    }
}

public class Topping
{
    public Topping(string description, double price)
    {
        Description = description;
        Price = price;
    }

    public double Price { get; private set; }
    public string Description { get; private set; }
}

用法

IPizza p = new Pizza(5.00);
p.AddTopping(new Topping("Pepperoni", 0.50));
p.AddTopping(new Topping("Sausage", 0.50));
var charge = p.CalculateCost(); // charge = 6.00

Asaf David 16 年前

在这种情况下,我不会使用decorator模式。取而代之的是,我要一份比萨饼,上面有一套图片:

public interface ITopping {
    double cost();
}

这一套保证不会重复。现在,要计算披萨的成本,你要把它的基价加在所有配料成本的总和上