std::map of objects or object pointers?

Question

I have two options to create a std map. I can work with both the types of map.

1.    std::map<A, std::string>    
2.    std::map<A*, std::string>

where A is a class object

Later in the code I will have to perform a find operation.

1.    std::map<A, std::string>   myMap1;
          if(myMap1.find(A_obj) != myMap1.end())
          {
          }

2.    std::map<A*, std::string>   myMap2;
          if(myMap2.find(A_obj_ptr) != myMap2.end())
          {
          }

I want to know which one is recommend to create. In which of these two, would I not have to overload any operators in class A for find operation to work. Which of these would have problems on insert operation when any operators are not overloaded.

If it helps, this is class A

class A
{
    private:
        std::vector<std::string> m_member;

    public:
        A(std::vector<std::string> input);  
};

Answer 1

Note that these two samples are only functionally equivalent if A instances are singletons. Otherwise it's very possible that two A values which are equal in value but different in address. This would lead to different semantics.

Personally I prefer the std::map<A, std::string> version because the semantics of it are crystal clear. The keys have equality semantics and there is no potentially for a dangling or nullptr value. The std::map<A*, std::string> version comes with a host of questions for the developer looking through the code

• Who owns the key values?
• Are all instances of A singletons? If not how do I ensure the A I'm looking for is the A* value that is stored?
• When are the keys freed?