如何处理两个类似子类的继承？ [英] How to handle inheritance from two similar sub-classes?

问题描述

我在这个系列中使用了前两个视频了解一些基本的OOP概念。

I've used the first two videos in this series to learn about some basic OOP concepts.

最近，我主要是在Node中写的，所以我在前端和后端使用原型继承。但是，这些教程使用Java展示了OOP概念。 Java是一种严格类型的语言，它使用经典继承。

Lately, I primarily write in Node, so I'm working with prototypical inheritance on the front-end and back-end. However, these tutorials showcase OOP concepts with Java. Java is a strictly-typed language which utilizes classical inheritance.

这个问题属于经典和原型继承，但方式不同。

This question pertains to both classical and prototypical inheritance, but in different ways.

这个问题有点难以理解，所以我将使用一个例子：

This problem is a little bit difficult to put into words, so I'll use an example:

我创建了一个名为动物的超类即可。然后我创建了两个动物子类：马和驴。现在我的程序需要两个子类的混合。创建 mule 实际上似乎有点棘手。

I've created a super-class called animal. I then create two sub-classes of animal: horse and donkey. Now my program requires a hybrid of the two sub-classes. Creating a mule actually seems to be a little tricky.

起初答案似乎很明显;创建一个独立的骡子类。但那种打败了OOP的目的。当我已经具有这些特征时创建一个新的子类是违反DRY原则。

At first the answer seemed obvious; create a stand-alone mule sub-class. But that kind of defeats the purpose of OOP. Creating a new sub-class when I already have the traits is a violation of the DRY principle.

要确认这是创建 mule 的合适方式，我问自己两个问题：

To confirm that this is an appropriate way to create my mule I asked myself two questions:

1）骡子是马吗？

2）骡子是驴吗？

答案似乎是一种响亮的种，倾向于是。

The answer seemed to be a resounding kind of that leans towards a yes.

我完全不知道如何用经典继承来实现这一点。我无法想出我认为具有接口或抽象类的好解决方案。

I'm completely lost as to how this would be accomplished with classical inheritance. I could not come up with what I considered a "good" solution with interfaces or abstract classes.

使用的语言典型的继承就像JavaScript一样，我可能只通过拉下应用于 mule 的方法和实例变量来选择性地繁殖骡子。然而，这似乎与创建一个全新的子类非常接近。

In a language which use prototypical inheritance like JavaScript, I might "selectively breed" a mule by pulling down only the methods and instance variables that applied to a mule. However, this seems to be rather close to creating a brand-new sub-class.

在经典和原型中处理此问题的正确方法是什么？ strong>继承？

What is the "correct" way to handle this problem in both classical and prototypical inheritance?

推荐答案

您正在寻找的概念是特征（您实际上提到过它） 。我将使用一个不同的例子，我觉得更合适：

The concept you are looking for is traits (you actually mentioned it). I will use a different example, that I find more appropriate:

trait Engine {
    public function startEngine() {
        echo 'Vrooom';
    }
}

trait Saddle {
    public function rideOnSaddle() {
        echo 'I feel the wind';
    }
}

interface Vehicle {
    public function go();
}

class Car extends Vehicle {
    use Engine;

    public function go() {
        echo $this->startEngine();
    }
}

class Bike extends Vehicle {
    use Saddle;

    public function go() {
        echo $this->rideOnSaddle();
    }
}

class Motorcycle extends Vehicle {
    use Engine;
    use Saddle;

    public function go() {
        echo $this->startEngine();
        echo $this->rideOnSaddle(); 
    }
}

进一步阅读： PHP中的特征， Javascript中的特征。

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