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std::map initialization

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sfx81    131
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

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SiCrane    11839
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]));

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theOcelot    498
A private lazy global.
class A{
static std::map<int, int>& MyMap();
void Foo(){
MyMap()[17] = 42;
//do other foo with MyMap();

std::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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