Question

Suppose I have a class Foo, with a private variable bar_ containing some state for Foo. If necessary, I may write public get/set methods for bar_. Naturally, I avoid this as much as possible to maintain encapsulation.

Assuming I have these get/set methods, whenever I have to access or modify bar_ within a method belonging to Foo, I usually do it directly to bar_, instead of using the get/set methods, which I use for accessing bar_ from outside the class. I have no justification other than concerns regarding the speed of directly accessing the variable versus calling the methods, but I suspect that if the get/set methods are defined inline (which they are) it shouldn’t make a difference. Does it make a difference? Does constness play a role in this?

So far I haven’t had any problems with this, but I have a lingering feeling I am Doing It Wrong. Are there any compelling arguments for not doing it? Any guidelines regarding this?

Answer 1

I have no justification other than concerns regarding the speed of directly accessing the variable versus calling the methods, but I suspect that if the get/set methods are defined inline (which they are) it shouldn’t make a difference. Does it make a difference? Does constness play a role in this?

The inline keyword hardly plays a role in whether or not the compiler does any inlining. The use for the keyword in that regard is essentially deprecated. Modern compilers inline like crazy, and they know when to do it better tan any programmer does.

Any compiler worth dirt will say “Hm, call this function to get this member variable; hey I can just get the member variable!” You’re worrying about nothing. This happens regardless of any inline keywords.

That said, I almost always use the member functions. If I change how a variable behaves when it’s accessed, I now “automatically” apply that everywhere it’s used. Clean code should be your goal, though, not a dogmatic “always skip functions” or not.

Anytime I just want a variable value, I use the corresponding member variable. (i.e, if I were writing std::vector, if I needed to check if the size was less than something, I’d say size() < x). But if it’s cleaner to use the variable directly, do that instead, such as mSize++.

const-ness is irrelevant. If you’re in a non-const function, you’ll use the non-const version of your getter, same with const. Obviously, using the members directly maintains const-ness. There is no difference.