Question

I was trying to learn some operator overloading methods on C++ then I had this error :

Error 7 error C2228: left of ‘.values’ must have class/struct/union

There is also another error that says :

Error 4 error C2065: ‘sum’ : undeclared identifier

Matrix<type> Matrix<type>::operator+(const Matrix& m){

    if(num_of_rows != m.num_of_rows || num_of_cols != m.num_of_cols) // Checking if they don't have the same size.

    Matrix<type> *sum;
    sum = new Matrix<type>(num_of_rows, num_of_cols);

    for(int i = 0; i < num_of_rows; i++)
        for(int j = 0; j < num_of_cols; j++)
            sum.values[i][j] =  values[i][j] + m.values[i][j];

    return *sum;
}

Can someone tell me where I did wrong?

Answer 1

In the code you have posted, sum is a pointer. Therefore, to access the members of the object, you need to use ->:

sum->values[i][j] = ...

You also seem to be missing a semicolon after the declaration Matrix<type> *sum;, but it’s unclear whether that is a transcription error or whether your code really looks like that.

Finally, your memory management leaks an object. You allocate an object with new, but return a copy of that object, and never free it. Perhaps you want something like:

Matrix<type> sum(num_of_rows, num_of_cols);

for ( ... )
    sum.values[i][j] = ..

return sum;