In C++11, can do this to initialize an object without using initialization list:
class Z{
int a=0;
int b;
z():b(0){} //<-- a already initialized
};
What I'm wondering is for class types, which of these is preferable:
class Z{
std::vector<int>a=std::vector<int>();
//or instead:
std::vector<int>a();
int b;
z():b(0){} //<-- a already initialized
};
There is no need to explicitly default initialize a, since it will be default constructed. This will do fine:
class Z
{
std::vector<int> a;
int b = 0;
z() {} //<-- a, b already initialized
};
Note that your second variant is a function declaration, not an initialization:
// function a(), returns std::vector<int>
std::vector<int> a();
so what you should have used is
// data member a is an std::vector<int>. Default construct it.
std::vector<int> a{};
Of course, if you do not want default construction, then this initialization at the point of declaration is very handy:
std::vector<int> a{0,1,2,3};
std::vectorbe default-constructed doesn't mean it is uninitialized. If a type has a default constructor which sets up a valid state, letting that one be called implicitly seems to me like the clearest option.
My recommendation would be to do this:
class Z{
std::vector<int> a;
int b = 0;
};
This is the shortest version and also the easiest to read. It doesn't add any useless clutter and makes it quite obvious that you're default-constructor a and initializing b to 0.
