Compile with: g++ main.cpp Test.cpp

main.cpp

#include <string>
#include "Test.h"

int main() {
  Test item = Test();
  std::string hello = "Hello World";
  item.setMessage(&hello);
  item.putMessage();
  return 0;
}

Test.cpp

#include "Test.h"

Test::Test() {}
void Test::setMessage(std::string* message) {
  this->message = message;
}
void Test::putMessage() {
  std::cout << *this->message;
}

Test.h

#include <iostream>

class Test {
  private:
    std::string* message;

  public:
    Test();
    void setMessage(std::string* message);
    void putMessage();
};