Static, private member of a class internal type

Question

I've a class myClass that has a type defined in it, myType, and a static const std::map that uses this type. How must I initialise the member?

The situation is like this. The compiler tells me: multiple definition of MyClass::myMap. But there is really only one definition. Is this initialisation (schematically) correct?

class myClass
{
  struct myType
  {
    // ...
  };
  static const std::map<int, myType> myMap;
};

const std::map<int, myType> myClass::myMap = {
  {1, {"hello myType", 99, "woops"}},
  {2, {"hello again", 66, "holla"}},
  {3, {"and bye", 33, "adios"}}
};

It's not a duplicate because the const members in the proposed question are not static.

Also this question: Initializing private static members does not answer the question since the static const members are int's.

Is it really `const myClass::std::map myMap` and not `const std::map myClass::myMap`? The first one shouldn't compile because there is no `myClass::std::map`. — user253751, Oct 04 '16 at 21:42
I fixed them both, it was not present in my code and thus not the problem. — dani, Oct 04 '16 at 21:50
Add myClass like so : `const std::map myClass::myMap = {` Compiles for me. — doug, Oct 04 '16 at 22:21
Your sampe initialization is correct but it needs to not be in a header file — M.M, Oct 05 '16 at 02:09

score 2 · Accepted Answer · answered Oct 05 '16 at 04:04

As written, both the declaration and definition are in the same file. If you do this, and you "#include" the file in more than one place, there will be multiple definitions created.

The static value is typically initialized separately, in a C++ source file and not in the header file with the class.

Static, private member of a class internal type

1 Answers1