std::map initialization
Author
Hi All. I was wondering if there is any other way to initialize static map member.
e.g
std::map<int,int> A::MyMap;
class A
{
public :
A()
{
static bool mapInit = false;
if ( !mapInit )
{
mapInit = true;
MyMap[0] = 100;
MyMap[1] = 200;
...
}
}
static std::map<int,int> MyMap;
};
Thanks , Kazz
Yeah, there are other ways. One example:
class A { public : static std::map<int,int> MyMap;};std::pair<int, int> initializers[] = { std::pair<int, int>(0, 100), std::pair<int, int>(1, 200)};std::map<int,int> A::MyMap(initializers, initializers + sizeof(initializers)/sizeof(initializers[0]));
A private lazy global.
You may also be able to just make a plain lazy global in A.cpp, so it doesn't even have to be part of the class declaration, depending on how it's used.
//A.hclass A{ static std::map<int, int>& MyMap(); public: void Foo(){ MyMap()[17] = 42; //do other foo with MyMap(); }};//A.cppstd::map<int, int>& A::MyMap(){ static std::map<int, int> map; static bool initialized = false; //initialize the map, if it hasn't been already if(!initialized){ //you may also be able to use the map's empty() member to check. //fill it in map[0] = 100; map[1] = 200; } return map;}You may also be able to just make a plain lazy global in A.cpp, so it doesn't even have to be part of the class declaration, depending on how it's used.
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