C++ error A nonstatic member reference must be relative to a specific object

Question

I am trying to call a function on an object, but I'm getting this error. I have two classes: a Sudoku class and a Puzzle class. The Sudoku class inherits the Puzzle class. The Sudoku class has protected variable, a 2D array of Puzzle objects Puzzle libraryOfPuzzles[4][10]; When I try to call the setSolution function on a the libraryOfPuzzles[][]; , it doesn't work. However, when I call it on a Puzzle test[4][10]; that is created inside the function itself, it works. Why is this?

void Sudoku::createLibraries(string name) {
    Puzzle test[4][10]; //added for demonstration purposes
    string fileName = "";
    int i = 0;
    for (int k = 0; k < 40; k++) {
        fileName = name + to_string(k) + ".txt";
        string aWord;
        ifstream fin;
        fin.open(fileName);
        i = 0;
        int value = 0;
        while (!fin.eof()) {
            fin >> aWord;
            int value = stringToInt(aWord);
            libraryOfPuzzles[k / 10][k % 10].setSolution(i / 9, i % 9, value); //this line gives error
            test[k / 10][k % 10].setSolution(i / 9, i % 9, value); //this line is fine
            i++;
        }
    fin.close();
    }
}

Include the full error message in your question, and show how you declare `libraryOfPuzzles`. — super, May 20 '18 at 20:42
https://stackoverflow.com/questions/5605125/why-is-iostreameof-inside-a-loop-condition-considered-wrong — M.M, May 20 '18 at 20:51

score 0 · Accepted Answer · answered May 20 '18 at 20:43

0

createLibraries cannot be defined as static.

answered May 20 '18 at 20:43

Ali Asadpoor

327
1
13

This fixed it. Thank you! Why can't createLibraries be defined as static? – Roy K. May 20 '18 at 21:11
Because `libraryOfPuzzles` is a non-static member variable so to access it you need a valid `this` pointer, which static methods do not have. The error message from the compiler could be a little less cryptic but this is pretty elementary stuff. – Paul Sanders May 20 '18 at 23:34

score 0 · Answer 2 · answered May 20 '18 at 20:44

0

I think you problem is that you array is not public. So libraryOfPuzzles[][]; can't access it but Puzzle test[4][10]; can.

Hopes this helps.

answered May 20 '18 at 20:44

EP1X WARR10R

49
8

I changed it to public but same problem. – Roy K. May 20 '18 at 21:09

C++ error A nonstatic member reference must be relative to a specific object

2 Answers2