C ++重载括号[]运算符get＆set不同的返回类型

Question

I'm trying to overload the [] operator for a class that I created with different return types for the getter and setter.

I want the setter to return a reference to a another class instance, which is happening fine at the moment, the problem is that I want the getter to return a char, but in my main when i'm assigning char c = object[5] it's calling the setter instead of the getter and returning the wrong return type.

That how it looks in my code:

Board.h

const char& operator[](Board_Node index) const;
Board_Node& operator[](Board_Node index);

Board.cpp

const char& Board::operator[](Board_Node index) const
{
    int boardIndex = index.i * _boardSize + index.j;
    if (boardIndex < 0 || boardIndex >= _board.size())
    {
        throw IllegalCoordinateException(index.i, index.j);
    }
    return _board[index.i * _boardSize + index.j].token;
}

Board_Node & Board::operator[](Board_Node index)
{
    int boardIndex = index.i * _boardSize + index.j;
    if (boardIndex < 0 || boardIndex >= _board.size())
    {
        throw IllegalCoordinateException(index.i, index.j);
    }
    return _board[index.i * _boardSize + index.j];
}

main.cpp

char c = board1[{1, 2}]; cout << c << endl;

That line results in error: no suitable conversion function from "Board_Node" to "char" exists.

Already tried all forms with const everywhere and nothing worked.

Appericiate any help, thank you!

Answer 1

Calling the overloaded functions getters and setters based on whether an object is const or non- const is not appropriate.

The non- const version of the overload is given higher priority if the object is not const .

I suggest adding an explicitly named getter function, which can use the overloaded operator[] function.

char get(Board_Node index) const
{
   return (*this)[index];
}

---

As a matter of good practice, it will be better to change the return type of the const version of the operator[] function to return Board_Node const& .

Board_Node const& operator[](Board_Node index) const;
Board_Node& operator[](Board_Node index);

That will allow you to extract other information from the corresponding Board_Node , not just a char .

With that, you won't need the 'get function. You'll have to change usage of the function. You'll have to change usage of the operator[]` function a bit.

char c = board1[{1, 2}].token;
cout << c << endl;