Does it make sense to provide non-const reference getter

Question

Sometimes I need to expose some of the class members. For example in the following example class Mechanic may need direct access to Engine componen

Answer 1

Explicit getters and setters can be overly-bureaucratic; it depends on your situation.

The main cited reason for having getter and setter functions is that it isolates the clients of your class from potential changes in implementation in the future (for instance, consider what would happen if you decide to generate an Engine object on demand (rather than using a member variable), or decide to hide it behind a smart pointer, or some other container).

If your class if very simple (e.g. close to being a POD) and unlikely to change, then it may not be worth the faff of having to implement the getters and setters.

However, to answer your question, a non-const getter probably doesn't make much sense. Your getter prototype should be Engine & engine() const; otherwise you won't be able to call it on const Car objects.