Question

Why does my map inside Test does not return its value? What’s wrong with this?

class Test{ //Test.h
public:
  std::map< char*,  int> mm;

  Test();
  void set();
  int get( char*);
};

Test::Test(){ //Test.cpp
}

void Test::set(){
  mm["aaa"] = 24;
}

int Test::get( char* n){
  return mm[n];
}

int main(){ //main.cpp
   Test *test = new Test();
   test->set();

   //this returns 0 instead of 24
   printf("From Test: %d\n", test->get("aaa"));
   printf("From Test: %d\n", test->mm["aaa"]);

   delete test;

   //this map works
   std::map<char*, int> mm;
   mm["a"] = 54;

   printf("Local: %d\n", mm["a"]);

   return 0;
}

Needs extra text to post >.<

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Answer 1

It fails because you use char* pointer as a key. For two literals addresses will be different. To make map work properly you must use some other string class which has operator< defined. std::string, for instance.