Default parameters with C++ constructors [closed]

Solution 1:

Definitely a matter of style. I prefer constructors with default parameters, so long as the parameters make sense. Classes in the standard use them as well, which speaks in their favor.

One thing to watch out for is if you have defaults for all but one parameter, your class can be implicitly converted from that parameter type. Check out this thread for more info.

Solution 2:

I'd go with the default arguments, especially since C++ doesn't let you chain constructors (so you end up having to duplicate the initialiser list, and possibly more, for each overload).

That said, there are some gotchas with default arguments, including the fact that constants may be inlined (and thereby become part of your class' binary interface). Another to watch out for is that adding default arguments can turn an explicit multi-argument constructor into an implicit one-argument constructor:

class Vehicle {
public:
  Vehicle(int wheels, std::string name = "Mini");
};

Vehicle x = 5;  // this compiles just fine... did you really want it to?