抽象类与接口 [英] Abstract Class vs. Interface

问题描述

我已经在 SO 以及网络的其他部分搜索了一个很好的答案，但我还没有找到我真正理解的答案.我将以不同的方式呈现这个，希望答案也能帮助其他人.

I have searched around SO as well as the rest of the web for a good answer but I have't found one that I really understand. I am going to present this in a different way and hopefully the answers will help others as well.

据我了解，这两个概念有相同的规则，只是抽象类由于方法实现能力更灵活.另外，我知道您可以实现多个接口并且只扩展一个类，但我确信与我提到的两个不同之处更多.

As far as I understand, the two concepts have the same rules except an abstract class is more flexible due to the method implementation ability. Also, I am aware you can implement multiple interfaces and only extend a single class but I'm sure there are more differences than the two I mentioned.

请查看这两个代码片段，并举例说明我可以用每个示例做什么来让我想要或不想使用另一个.

Please look at the two snippets of code and give me an example what I can do with each of my examples that would make me want or not want to use the other.

abstract class Foo {
    abstract public function getValue();
    abstract public function setValue($value); 
}


class myObj extends Foo {
    function getValue() {

    }
    function setValue($value) {

    }
}

界面

interface Foo {
    public function getValue();
    public function setValue($value);
}

class myObj implements Foo {
    function getValue() {

    }
    function setValue($value) {

    }
}

推荐答案

恢复思路(全局，不详细):

To resume the idea (globally, not in detail):

inheritance

是从某物扩展的概念，并且可以选择添加一些新功能或覆盖一些现有功能(以不同的方式).但是使用继承，您与父级共享大部分代码.您是父母+其他一些东西.

is the notion to extend from something, and optionally add some new feature or override some existing feature (to do differently). But using inheritance, you share a big part of code with the parent. You are a parent + some other things.

interface

代表一些能力(我们说一个类正在实现一个接口来表示它具有这些能力).一个接口可以由两个完全不同的类来实现，并且不共享它们的代码(它们实现的方法除外).当 A 和 B 实现接口 C 时，A 不是 B，B 也不是 A.

is representing some abilities (we says a class is implementing an interface to says that it has these abilities). An interface can be implemented by 2 classes which are completely different and do not share their code (except for methods they implements). When A and B are implementing interface C, A is not a B and B is not a A.

interface 的原因之一确实是让程序员可以做与多继承一样的事情，但没有多继承问题.

And one of the reason for interface is indeed to allow programmer to do the same as they could do with multi-inheritance, but without multi-inheritance problems.

这个概念在一些编程语言中使用，比如 JAVA、PHP...

This notion is used in some programming languages like JAVA, PHP...

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