C ++：重载读取和写入访问的[]操作符 [英] C++: Overloading the [ ] operator for read and write access

问题描述

一般来说，你如何为读和写访问声明一个类的索引 [] ？

In general, how do you declare the index [ ] operator of a class for both read and write accesss?

我尝试过

/**
 * Read index operator.
 */
T& operator[](T u);

/**
 * Write index operator
 */
const T& operator[](T u);

这给我错误

../src/Class.h:44:14: error: 'const T& Class::operator[](T)' cannot be overloaded
../src/Class.h:39:8: error: with 'T& Class::operator[](T)'

推荐答案

可变版本很好：

T& operator[](T u);

但是 const code> const 成员函数以及返回 const 引用：

but the const version should be a const member function as well as returning a const reference:

const T& operator[](T u) const;
                         ^^^^^

这不仅区别于其他重载，允许（只读）访问您的类的 const 实例。一般来说，重载成员函数可以通过它们的参数类型和const / volatile限定条件来区分，但不是的返回类型。

This not only distinguishes it from the other overload, but also allows (read-only) access to const instances of your class. In general, overloaded member functions can be distinguished by their parameter types and const/volatile qualifications, but not by their return types.

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