Shared instance with dictionary (c++)

Question

I'm C++ newbie here. I'm trying to implement something. My goal is simple:

1. A shared instance which can be easily accessed in different scopes.
2. This shared instance has a dictionary instance variable (map) to store key-value pair data.
3. We can add a new key-value pair or get the value for a key via the public accessor.

Here is my header:

// .h
using namespace std;

class Person;
typedef map<string, Person> DictForPeople;

class Company {
    Company();
    void setValueForKey(string key, Person value);
    Person valueForKey(string key);
private:
    DictForPeople _dictForPeople;
};

class Person {
public:
    Person();
    void setName(string name);
    string name();
private:
    string _name;  // !!!: raise error here
};

and the implementation (.cpp):

// .cpp
Company::Company(){

}
void Company::setValueForKey(string key, Person value){
    _dictForPeople[key] = value;
}
Person Company::valueForKey(string key){
    return _dictForPeople[key];
}
Person::Person(){

}
void Person::setName(string name){
    _name = name;
}
string Person::name(){
    return _name;
}

I'm trying to use singleton pattern, but it raises a lot of compilation errors. How to correctly declare a shared instance with accessors for string/map?

---

UPDATE 1:

The above code raises an error: Implicit instantiation of undefined template 'std::__1::basic_string, std::__1::allocator >'

The environment is Xcode 6/Mac OS X 10.10 with LLVM/Clang. I'm trying using C++ instead of Objective-C for some reasons.

---

UPDATE 2:

My implementation with Singleton Pattern is the following (reference):

// .h
using namespace std;

class Person;
typedef map<string, Person> DictForPeople;

class Company {
    static Company& getInstance() {  // For Singleton Pattern
        static Company instance;
        return instance;
    }

    void setValueForKey(string key, Person value);
    Person valueForKey(string key);
private:
    Company() {};  // For Singleton Pattern
    Company(Company const&);  // For Singleton Pattern
    void operator=(Company const&);  // For Singleton Pattern

    DictForPeople _dictForPeople;
};

class Person {
public:
    Person();
    void setName(string name);
    string name();
private:
    string _name;  // !!!: raise error here
};

This change raises more errors:

1. Field has incomplete type 'Person': this could be fixed by moving the class declaration Person above the class declaration Company.

2. Other errors are the same message introduced before (Implicit instantiation of undefined template 'std::__1::basic_string, std::__1::allocator >') but in different places. The C++ file utility LLVM

   template <class _T1, class _T2>
   struct _LIBCPP_TYPE_VIS_ONLY pair
   {
       typedef _T1 first_type;
       typedef _T2 second_type;
   
       _T1 first;     // <<<-- raise the error here
       _T2 second;
   
       // pair(const pair&) = default;
       // pair(pair&&) = default;
   
       _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR pair() : first(), second() {}
   

---

Update 3:

I forgot to mention that the above code is embedded in extern "C" {...} block.

Answer 1

You code seems fine to me.

Did you included string and map in your header file? If yes, please also provide the compilation error's.