compile error about member variable initialization

Hello everyone,


Why the below code segment will result in compile error? When I change code to the comment one (constructor), it can compile. The compiler is too stupid? :-)

I am using Visual Studio 2005.

--------------------
main.cpp(13) : error C2758: 'Foo::vi' : must be initialized in constructor base/member initializer list

see declaration of 'Foo::vi'
--------------------

Code:

#include <vector>

using namespace std;

class Foo {

private:

	vector<int>& vi;

public:

	Foo (vector<int>& vi_in)
	{
		vi = vi_in;
	}
/*
	Foo (vector<int>& vi_in) : vi (vi_in)
	{
	}
*/
};

int main()
{
	vector<int> vi;
	Foo foo = Foo (vi);


	return 0;
}

thanks in advance,
George

The compiler is right. References must be initialized and assignment (in constructor body) is not initialization.

Regarding having a reference member: the vector outside the class must have a longer lifetime than Foo, or the member reference becomes invalid.

To do that, you need to use a pointer (or just taking a copy of the object). References aren't perfect -_-

Originally Posted by Elysia

To do that, you need to use a pointer (or just taking a copy of the object). References aren't perfect -_-

I don't think there's any real problem. If you need a "reseatable" reference then use a pointer, but in this case I think it's a simple case of "Just wasn't doing it right."

Yeah, you could probably get away with references here since the OP is passing the array in the constructor. But if you need to assign the vector member at a later stage than the constructor, a pointer is necessary; otherwise the code is perfectly fine.