Question

Sometimes, for certain things like writing a line to a console, feels like something that should be globally accessible to all objects. Something like:

writeError("UNHANDLED EXCEPTION",someData);

Also things such as math functions feel this way too. But how do you draw the line when doing this sort of thing becomes bad practice?

Answer 1

Some people draw the line at the point where the non-member function needs to be a friend of one of its arguments, so they use a lot of free functions.

Some people draw the line at the point where the non-member function could reasonably be a member function of one of its arguments, even though it doesn’t actually use the class internals. They have somewhat fewer free functions.

It’s usually best not to think of this as “becoming bad practice” – not all design in C++ is “properly” object-oriented. If your task is best solved by means other than OOP, then using OOP is itself “bad practice”. The argument how best to design your code can go on indefinitely in any language, but C++ doesn’t make any particular effort to steer you towards writing classes.

See also:

Effective C++ Item 23 Prefer non-member non-friend functions to member functions