Weird behavior with OOP and string pointers - c++

Question

Here's my code:
#include <iostream>
#include <string>
class Human
{
public:
std::string * name = new std::string();
void introduce();
};
void Human::introduce()
{
std::cout << "Hello, my name is " << Human::name << std::endl;
}
int main()
{
Human * martha;
martha->name = new std::string("Martha");
martha->introduce();
return 0;
}
Well, it's supposed to print a message out like:
"Hello, my name is Martha" but it doesn't print neither the "Hello, my name is" string or the "Martha" name. Why does it occur?

Answer 1

The fix is simple and is to completely remove all pointers; see the code below. There are a number of issues with your code that I could address in detail, including memory leaks, uninitialized variables, and general misuse of pointers, but it seems that you're possibly coming from a different language background and should spend time learning good practice and the important semantics and idioms in modern C++ from a good C++ book.
#include <iostream>
#include <string>
class Human
{
public:
std::string name;
void introduce();
};
void Human::introduce()
{
std::cout << "Hello, my name is " << name << std::endl;
}
int main()
{
Human martha;
martha.name = "Martha";
martha.introduce();
return 0;
}

Answer 2

Few modifications are required to the code.
Updated code along with the comments to the change made are included below.
#include <iostream>
#include <string>
class Human
{
public:
//Removed pointer to a string
//Cannot have an instantiation inside class declaration
//std::string * name = new std::string();
//Instead have a string member variable
std::string name;
void introduce();
};
void Human::introduce()
{
//Human::name not required this is a member function
//of the same class
std::cout << "Hello, my name is " << name << std::endl;
}
int main()
{
Human *martha = new Human();
//Assign a constant string to string member variable
martha->name = "Martha";
martha->introduce();
return 0;
}
As suggested by #alter igel - The Definitive C++ Book Guide and List would be a good place to start.

Answer 3

#include <iostream>
#include <string>
class Human {
public:
void Human(std::string* n) { name = n; }
void introduce();
private:
std::string* name;
};
void Human::introduce() {
std::cout << "Hello, my name is " << name << std::endl;
}
int main() {
Human* martha = new Human(new std:string("Martha"));
martha->introduce();
return 0;
}
Try that. The difference is that you don't initialise the variable in the class definition, and you initialise the name with the constructor. You can split the method definition out into it's own section, but it's only one line and is fine being inside the class definition.