子类专用属性的设计模式 [英] Design pattern for specialized properties in subclasses

问题描述

重复的 C＃访问子类属性我们有一个对象模型，其中每个对象都有一个父项，而我想要访问父属性。

Duplicate of C# Accessing a subclass property - see additional solution approaches there.

与每个对象的具体类型。例如车轮应具有Car类型的母体属性。我的猜测是，有一个已经建立的设计模式来实现这一点（在.NET中）。然而，我没有找到它，所以我想出的设计看起来像这样

I have an object model where each object has a parent and I would like to access the parent property with the specific type for each object. So e.g. Wheel shall have a parent property of type Car. My guess is that there is an established design pattern for achieving this (in .NET). However, I have not found it so the design I came up with looks like this

public class BaseObject<T> where T : BaseObject<T>
{
    private T mParent;
    protected T Parent
    {
        get { return mParent; }
    }

    public BaseObject(T parent)
    {
        mParent = parent;
    }

    public void Save() ...
    public void Delete() ...
    public BaseObject<T> Clone() ...
}

public class Car : BaseObject<Car>
{
    public Car(Car parent) : base(parent)
    {
    }

    public bool Is4WD()
    {
        return true;
    }
}

public class Wheel : BaseObject<Car>
{
    public Wheel(Car parent) : base(parent)
    {
    }

    public float RequiredTirePressure()
    {
        return Parent.Is4WD() ? 3.0f : 2.5f;
    }
}

您是否看到这种方法有任何设计或性能缺陷？你可以推荐一个更好的设计吗？

Do you see any design or performance drawbacks with this approach? Can you recommend a better design?

推荐答案

答案是使用组合而不是继承。车轮不是车，所以不应该从 Car 延伸。相反，请在其构造函数中使轮采取 Car 。

The answer is to use composition instead of inheritance. A wheel is not a car, so it should not extend from Car. Instead, have the Wheel take a Car in its constructor.

例如：

public class Wheel {
    private Car car;

    public Wheel(Car car) {
        this.car = car;
    }

    public float RequiredTirePressure() {
        return car.Is4WD() ? 3.0f : 2.5f;
    }
}

• 组合继承


• Composition over inheritance

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