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c++collectionsconstructorstaticinstances

Static Collection of Instances C++?

I have a class Phone, I want it, when created to add itself to a static collection of phones. So I have the collection:

static vector < class Phone* > instances;

And in the constructor I do this: 

Phone::instances.push_back(this);

But the linker throws an unresolved external symbol, why is that? What am I doing wrong? I didn't find a similar question. Is it necessary to add the instance outside the constructor? Or do I have to have the collection on another class? Thank you very much.

Solution

  • You must declare static member outside your class.

    In your header:

    class Phone{
...
static vector < class Phone* > instances;
...
};

    In your cpp you need to create the instance of it:

    //on global or namespace scope
vector <Phone*> Phone::instances;