朋友函数和朋友类之间有什么区别？ [英] what is the difference between friend function and friend class?

问题描述

朋友函数和朋友类之间有什么区别？应该使用friend关键字？

what is the difference between friend function and friend class? and where should be use of friend keyword?

推荐答案

简而言之，一个是类，一个是函数。对于函数，只有一个函数可以访问私有成员。对于一个类，整个类及其所有函数都可以访问对等类的私有成员。

In short, one is a class and one is a function. For the function, just that one function gets access to private members. For a class, the whole class and all its functions get access to the private members of the befriended class.

friend关键字用于授予对私有数据成员的访问权限。有时你可能需要一个帮助类或一个免费类来访问不同类的私有成员。对于函数，常见的例子是运算符过载。也许你想重载+运算符。您可以在类外声明一个运算符+函数（因此可以在没有对象的情况下调用它），并且需要访问私有类数据。

The friend keyword is used to grant access to private data members. At times you may need a helper class or a complimentary class to access the private members of a different class. For functions, a common example is an operator overload. Perhaps you want to overload the + operator. You may make an operator+ function declared outside the class (so it can be called without an object) and it will need to access the private class data.

签出此网站，以获取有关两者的详细说明以及如何使用它们。

Check out this site for a detailed description of both and how to use them.

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