constructors and dynamic arrays

[insanoflex312]

I have a 2 classes, class A and class B. Class A contains a pointer to a dynamically allocated array of class B's, created in Class A's constructor. I need to pass arguments to Class Bs' constructors when they are allocated. Is there any way to do this, or will I have to call some kind of Init() function? Hopefully this makes sense to someone.

[hamsterman]

When you allocate an array of dynamic memory, default constructors will be called. There is no way to make it call any other kind of constructor. I suppose Init would be the best option. Alternatively you could malloc and then placement-new, but that might be a mess.

[ne555]

Or use std::vector (reserve and push_back), so you don't have to worry about handling the memory.

[wasabi]

A useful trick is to write all of B's constructor code in Init() and then make the constructor simply call Init(). That way, should you make a change to the code later on, you only have to do it once.

[insanoflex312]

Thanks for the help, everyone. Vectors seems like the way to go, but I'll still move the constructor stuff into an Init() function for my classes.

[Athar]

You can create a vector filled with copies of a particular element:
vector<Foo> vec(n,Foo(42));

Whether that makes sense depends on the situation.