成员函数末尾的 const 是什么意思?

What is the meaning of a const at end of a member function?(成员函数末尾的 const 是什么意思?)

问题描述

C++ 中的 const 关键字写在成员函数的末尾(参数列表之后)究竟是什么意思?

What exactly does the const keyword in C++ mean when it's written at the end of a member function (after the argument list)?

推荐答案

这意味着 *this 是该成员函数内部的 const ，即它不会改变对象.

It means that *this is const inside that member function, i.e. it doesn't alter the object.

关键字this 是prvalue 表达式，其值是调用函数的对象的地址.X 类的成员函数中this 的类型是X*.如果成员函数声明为const，则this 的类型为const X*.[第 9.3.2 节 §1]

The keyword this is a prvalue expression whose value is the address of the object for which the function is called. The type of this in a member function of a class X is X*. If the member function is declared const, the type of this is const X*. [section 9.3.2 §1]

在一个const成员函数中，调用该函数的对象是通过一个const访问路径访问的；因此，const 成员函数不得修改对象及其非静态数据成员.[第 9.3.2 节 §2]

In a const member function, the object for which the function is called is accessed through a const access path; therefore, a const member function shall not modify the object and its non-static data members. [section 9.3.2 §2]

这意味着可以在类的 const 实例上调用 const 成员函数.不能在 ^{[1]const 对象上调用非 const 成员函数，因为它可能会尝试修改它.}

This means that a const member function can be called on a const instance of the class. A non-const member function can't be called on ^[1]a const object, since it could potentially try to modify it.

<支持>^[1] 注意:临时不是 const 对象，除非它是 const 类型.

^{[1] Note: a temporary is not a const object unless it's of const type.}

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