How can I use static members in friend functions without prefixing [class name]::

Question

I have this code in Player.h

class Player {
  friend void clearBoard();

private:
  static char board[4][4][4];
};

and this code in Player.cpp

char Player::board[4][4][4] = {};

void
clearBoard() {
  for (byte i = 0; i < 4; i++)
    for (byte j = 0; j < 4; j++)
      for (byte k = 0; k < 4; k++)
        board[i][j][k] = ' ';
}

so during compilation I get an error

Player.cpp:37:9: error: ‘board’ was not declared in this scope
   37 |         board[i][j][k] = ' ';
      |         ^~~~~

I use board literally hundred other times in the Player.cpp and using Player:: with each one will negatively affect readability an my nerves.

Is there a way to escape this hell?

I have tried

using Player::board;
using Player::board[][][];
Enclosing my class with namespace, then using that namespace.

without any effect.

All suggestions except

"just redefine clearBoard() as static"

will be greatly appreciated.

"using `Player::` with each one will negatively affect readability" -- no, it won't. Just do it. — Pete Becker, Jun 22 '20 at 19:14
if a name of a variable is too long you can always do `auto& x = some_super_long_variable_name;`. Though, typing less != readability. There is a reason you need to qualify where a name comes from — 463035818_is_not_an_ai, Jun 22 '20 at 19:27
you can use `inline` for `static` members with `c++17` instead of explicit initialization. outside the class — asmmo, Jun 22 '20 at 19:42

score 2 · Accepted Answer · answered Jun 22 '20 at 19:35

2

In general typing less is not a way to improve readability. Writing Player::board is good because if you write board outside of Player then it is not clear where it comes from. Having said this, you can always introduce an alias if a variable name is too long and you are too lazy to type its name repeadetely:

void
clearBoard() {
  auto& board = Player::board;
  for (byte i = 0; i < 4; i++)
    for (byte j = 0; j < 4; j++)
      for (byte k = 0; k < 4; k++)
        board[i][j][k] = ' ';
}

Just make sure to keep the scope of the alias short and in this specific example I fail to see the benefit (introducing the alias is more typing, not less).

answered Jun 22 '20 at 19:35

463035818_is_not_an_ai

109,796
11
89
185

https://github.com/zzaba/3D_Tic-Tac-Toe/blob/master/Player.cpp Here, in status() I use board 84 times. – beardeadclown Jun 22 '20 at 19:57
@beardeadclown and? Writing `Player::` 84 times makes it obvious at a blink that those 84 `board`s come from `Player` – 463035818_is_not_an_ai Jun 22 '20 at 20:02
Can you recommend any books/guidelines for good coding practices like that? – beardeadclown Jun 22 '20 at 20:06
1

@beardeadclown here https://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list and https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines – 463035818_is_not_an_ai Jun 23 '20 at 09:24

How can I use static members in friend functions without prefixing [class name]::

1 Answers1