/**? a.cpp 的內(nèi)容如下:
?* 類的靜態(tài)成員變量.
?*? 編譯鏈接命令
?*? g++ -o a.out a1.cpp -std=c++11
?*
?*/

#include <iostream>
#include <string>
#include <map>

namespace tiao{

?? ?class A {
?? ??? ?public:
?? ??? ?static std::map<std::string, int> map1;
?? ??? ?static std::map<std::string, int> map2;
?? ??? ?int some_int;
?? ?};
};
/**
?* 如果注釋調(diào)下面兩行，編譯時會報錯:
?* Undefined symbols for architecture arm64:
? "tiao::A::map1", referenced from:
????? _main in a1-b57425.o
? "tiao::A::map2", referenced from:
????? _main in a1-b57425.o
ld: symbol(s) not found for architecture arm64
?*/
std::map<std::string, int> tiao::A::map1;
std::map<std::string, int> tiao::A::map2;

int main(){
?? ??? ?tiao::A::map1.insert(std::make_pair(std::string("kshg"), 3));
?? ??? ?tiao::A::map2.insert(std::make_pair(std::string("ksh"), 3));
? ??? ?tiao::A? A1;
?? ??? ?auto it1 = tiao::A::map1.find(std::string("ksh"));
?? ??? ?if(it1 == tiao::A::map1.end()) {
?? ??? ??? ?std::cout<<"在map1 中沒有找到 ksh"<<std::endl;
?? ??? ?}
?? ??? ?auto it2 = tiao::A::map2.find("ksh");
?? ??? ?if(it2 != tiao::A::map2.end()) {
?? ??? ??? ?std::cout<<"在map2 中找到 ksh"<<std::endl;
?? ??? ??? ?std::cout<<"key: "<< it2->first << "; value: " <<it2->second <<std::endl;
?? ??? ?}

?? ??? ?return 0;
}