封装和抽象之间的确切区别是什么?


当前回答

这里的大多数答案都关注于OOP,但封装开始得更早:

Every function is an encapsulation; in pseudocode: point x = { 1, 4 } point y = { 23, 42 } numeric d = distance(x, y) Here, distance encapsulates the calculation of the (Euclidean) distance between two points in a plane: it hides implementation details. This is encapsulation, pure and simple. Abstraction is the process of generalisation: taking a concrete implementation and making it applicable to different, albeit somewhat related, types of data. The classical example of abstraction is C’s qsort function to sort data: The thing about qsort is that it doesn't care about the data it sorts — in fact, it doesn’t know what data it sorts. Rather, its input type is a typeless pointer (void*) which is just C’s way of saying “I don't care about the type of data” (this is also called type erasure). The important point is that the implementation of qsort always stays the same, regardless of data type. The only thing that has to change is the compare function, which differs from data type to data type. qsort therefore expects the user to provide said compare function as a function argument.

封装和抽象是密切相关的,因此您可以认为它们确实是不可分割的。就实际而言,这可能是对的;也就是说,这里有一个不太抽象的封装:

class point {
    numeric x
    numeric y
}

我们封装了点的坐标,但是我们没有实质性地将它们抽象出来,只是在逻辑上对它们进行分组。

这里有一个抽象的例子,它不是封装:

T pi<T> = 3.1415926535

这是一个具有给定值(π)的泛型变量pi,声明并不关心变量的确切类型。诚然,我很难在真实的代码中找到这样的东西:抽象实际上总是使用封装。然而,上面的内容在c++(14)中确实存在,通过变量模板(=变量的通用模板);使用稍微复杂一点的语法,例如:

template <typename T> constexpr T pi = T{3.1415926535};

其他回答

封装要求模块化。它要求您创建具有数据和处理数据的方法的对象。在这种情况下,您可以将其视为一个模块。

抽象为您提供了类的一般视图。

抽象是对用户隐藏无用的数据 封装是将数据绑定到一个胶囊(类)中。 我认为封装是我们实现抽象的方式。

简而言之

抽象使用->封装 & 封装使用->数据隐藏

OR

数据隐藏是封装和的子集 封装是抽象的一个子集

参考:http://www.tonymarston.co.uk/php-mysql/abstraction.txt

抽象是我们将要执行的实现的契约。实现可能会在一段时间内发生变化。各种实现本身可能隐藏,也可能不隐藏,而是隐藏在抽象后面。

假设我们在一个接口中定义了一个类的所有api,然后要求代码的用户依赖于该接口中定义的api。我们可以自由地改进或修改实现,但必须遵守设定的合同。用户与我们的实现没有耦合。

我们在抽象中暴露所有必要的规则(方法),规则的实现留给实现者实体,实现也不是抽象的一部分。正是签名和声明使抽象成为现实。

封装只是通过减少对状态和行为的访问来隐藏内部细节。封装的类可能有也可能没有定义良好的抽象。

java.util.List是java.util.ArrayList的抽象。使用非公共访问修饰符标记的java.util.ArrayList的内部状态是封装。

Edit Suppose a class Container.nava implements IContainer , IContainer may declare methods like addElement, removeElements, contains, etc. Here IContainer represents the abstraction for its implementing class. Abstraction is declaring the APIs of the class or a module or a system to the outer world. These APIs become the contract. That system may be or may not be developed yet. The users of the system now can depend on the declared APIs and are sure any system implementing such a contract will always adhere to the APIs declared, they will always provide tge implementation for those APIs. Once we are writing some concrete entity then deciding to hide our internal states is encapsulation

通过使用单个通用示例进行抽象和封装

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我们都用计算器来计算复杂的问题!