CODEWITHSUNDEEP
c++dictionary
user195488
user195488

Reputation:

Initialize a static private map as empty

I have a static map that is a private data member. How do I initialize it in the implementation file so that it's initial containers are empty? It is not const. It is important that nothing is in this container at start.

Upvotes: 10

Views: 33641

Answers (3)

Black
Black

Reputation: 5080

If you declare it in the class definition, then you have to define it in the implementation:

--- test.h ---

// includes and stuff...
class SomeClass
{
    private:
        static std::map<int,std::string> myMap;
};

--- test.cpp ---

std::map<int,std::string> SomeClass::myMap; // <-- initialize with the map's default c'tor

You can provide an initialization, too:

std::map<int,std::string> SomeClass::myMap = std::map<int,std::string>(myComparator);

Upvotes: 3

Nikolai Fetissov
Nikolai Fetissov

Reputation: 84169

Header:

class XXX {
private:
    static std::map<X,Y> the_map; // declares static member
// ...

Implementation file:

std::map<X,Y> XXX::the_map; // defines static member

That will insert a constructor call for your map into your program initialization code (and a destructor into the cleanup). Be careful though - the order of static constructors like this between different translation units is undefined.

Upvotes: 13

Linuxios
Linuxios

Reputation: 35803

How about this (if I understand you correctly):

std::map<T,T2> YourClass::YourMember = std::map<T,T2>();

Upvotes: 8

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