封装和抽象之间的确切区别是什么?
当前回答
封装把一些东西放在一个盒子里,给你一个窥视孔;这使你从混乱与齿轮。
抽象完全忽略了无关紧要的细节,比如物体是否有齿轮、棘轮、飞轮或核心;他们只是“走了”
封装的例子:
内裤 工具箱 钱包 手提包 胶囊 冷冻carbonite 一个盒子,上面有或没有按钮 一个墨西哥卷饼(严格来说,是卷饼周围的玉米粉圆饼)
抽象的例子:
“一组事物”是一种抽象(我们称之为聚合) “包含其他事物的事物”是一种抽象(我们称之为组合) “容器”是另一种“物装物”的抽象;注意,所有的封装示例都是不同种类的容器,但并不是所有的容器都展示/提供封装。例如,篮子是一种不封装其内容的容器。
其他回答
抽象或封装并不严格要求信息隐藏。信息可能会被忽略,但不一定要隐藏。
封装是一种将事物视为单一事物的能力,即使它可能由许多复杂的部分或思想组成。例如,我可以说我坐在一把“椅子”上,而不是指这把椅子上的许多不同部分,每个部分都有特定的设计和功能,它们精确地组合在一起,目的是让我的屁股舒适地离地板几英尺远。
Abstraction is enabled by encapsulation. Because we encapsulate objects, we can think about them as things which relate to each other in some way rather than getting bogged down in the subtle details of internal object structure. Abstraction is the ability to consider the bigger picture, removed from concern over little details. The root of the word is abstract as in the summary that appears at the top of a scholarly paper, not abstract as in a class which can only be instantiated as a derived subclass.
I can honestly say that when I plop my butt down in my chair, I never think about how the structure of that chair will catch and hold my weight. It's a decent enough chair that I don't have to worry about those details. So I can turn my attention toward my computer. And again, I don't think about the component parts of my computer. I'm just looking at a part of a webpage that represents a text area that I can type in, and I'm communicating in words, barely even thinking about how my fingers always find the right letters so quickly on the keyboard, and how the connection is ultimately made between tapping these keys and posting to this forum. This is the great power of abstraction. Because the lower levels of the system can be trusted to work with consistency and precision, we have attention to spare for greater work.
另一个例子:
假设我创建了一个不可变的Rectangle类,如下所示:
class Rectangle {
public:
Rectangle(int width, int height) : width_(width), height_(height) {}
int width() const { return width_; }
int height() const { return height_; }
private:
int width_;
int height_;
}
现在很明显,我已经封装了宽度和高度(访问受到某种限制),但我没有抽象任何东西(好吧,也许我忽略了矩形在坐标空间中的位置,但这是示例的缺陷)。
好的抽象通常意味着好的封装。
一个好的抽象例子是通用数据库连接类。它的公共接口与数据库无关,非常简单,但允许我对连接做我想做的事情。你看到了吗?这里还有封装,因为类内部必须有所有低级句柄和调用。
抽象—隐藏实现—在设计—使用接口/抽象类
封装—隐藏数据—在开发时—使用访问修饰符(公共/私有)
封装是将复杂性包裹在一个胶囊中,即类&因此封装… 抽象是一个对象区别于其他对象的特征。
抽象可以通过使具有一个或多个抽象方法的类抽象来实现。它只是一个特性,应该由扩展它的类来实现。 例如,当你发明/设计一辆汽车时,你定义了一个特征,比如汽车应该有4个门、刹车、方向盘等,所以任何使用这种设计的人都应该包括这些特征。实现并不是抽象的首要部分。它只会定义应该包含的特征。
Encapsulation is achieved keeping data and the behaviour in one capsule that is class & by making use of access modifiers like public, private, protected along with inheritance, aggregation or composition. So you only show only required things, that too, only to the extent you want to show. i.e. public, protected, friendly & private ka funda…… e.g. GM decides to use the abstracted design of car above. But they have various products having the same characteristics & doing almost same functionality. So they write a class which extends the above abstract class. It says how gear box should work, how break should work, how steering wheel should work. Then all the products just use this common functionality. They need not know how the gear box works or break works or steering wheal works. Indivisual product can surely have more features like a/c or auto lock etc…..
两者都很强大;但是使用抽象需要比封装更多的技能,没有抽象,更大的应用程序/产品就无法生存。
抽象和封装都是用来隐藏数据的。但是有很大的不同。
封装
封装是将数据和对数据进行操作的代码绑定或包装成一个称为Class的单元的过程。
封装在实现级别解决了问题。
在类中,可以使用私有或受保护的访问修饰符来隐藏数据。
抽象
抽象是隐藏无关细节的概念。换句话说,通过对用户隐藏不必要的细节,使复杂的系统变得简单。
抽象在设计层面解决了问题。
可以通过在Java中创建接口和抽象类来实现抽象。
在ruby中,你可以通过创建模块来实现抽象。
示例:我们使用(收集,映射,减少,排序…)方法的枚举模块与数组和ruby哈希。