How do I invoke non-default constructor for a member variable?

Question

I have a class which is something like this:

template<int SIZE>
class MyClass{
public:
    MyClass(int a, int b){}
}

and I want another class to have an instance of MyClass:

class X{
    MyClass<10>??   // How do I pass values to constructor args a and b?
}

but I am unsure how to pass the arguments in to the two-argument constructor when declaring the object as a member variable?

Which version of C++ are you using? C++11? Most likely, you should just do it where the object is constructed, not where it's declared. — David Schwartz, Mar 03 '16 at 19:25
Possible duplicate of [C++ How to Initialize member object?](http://stackoverflow.com/questions/28436820/c-how-to-initialize-member-object) — Slava, Mar 03 '16 at 19:27

score 10 · Accepted Answer · answered Mar 03 '16 at 19:28

10

If you are using C++11 or later, you can write

class X{
    MyClass<10> mcTen = {1, 5};
}

Prior to C++11 you would need to do it in a constructor's initializer list:

class X{
    MyClass<10> mcTen;
    X() : mcTen(1, 5) {
    }
}

answered Mar 03 '16 at 19:28

I remember reading somewhere that the "proper" format is `Type name { /* things */ }`, and the `=` version would be deprecated or removed. I can't find a source for that, though, so can you confirm or deny? – Nic Mar 03 '16 at 20:24

1 Answers1