Guidance with header and main template - seek best practice please

I'm new to C++ and was needing some help in terms of using the best coding practices. Basically I have creat开发者_Python百科ed my header file (character.h) with the following data:

using namespace std;

class character
{
    //available to all
    public:
        character();
        ~character(){};

        int getHP(){return hp;};
        int damage(int _damage);
        int levelUp(int _xp);

        void setHP(int _hp){hp = _hp;};
        string getName(){return name;};

    protected:
        int hp;
        string name;
};

class player:public character
{
    public:
        player();
        ~player(){};
    protected:
        string name;
        int lvl;
        int xp;
};

class enemy:public character
{
    public:
        enemy(string _name, int _hp);
        ~enemy(){};
    protected:
        string name;
        int lvl;
        int xp;
};

I was trying to generate the main file (main.cpp) from this data

#include "character.h"
player::player()
{
    cout << "\t\t\nPlease enter your name: \n\t\t";
    cin >> name;
};

int main()
{
    //some code
    return 0;
}

But I keep getting errors

"undefined reference to `character::character()"

Can someone please help me, why am I getting this error and also is this approach the best practice for the layout of this design?

You need to define the constructor(s) for character in your code file:

character::character():
  hp(10),
  name("default")
{
}
character::character (std::string name): hp(10) [...]
character::character (int hp): name("Default") [...]
character::character (std::string name, int hp) [...]

This makes sure that all your instance variables are defined.

Since you define a destructor, you must obey the rule of three and define a copy constructor and assignment operator as well.

On a side note, you should use a convention to name your class/instance variables: myName, _name, or name_ are quiet common. Using cppcheck may save you some time/hassle as well.

What you need to do is create the definition for your default constructors character::character() and player::player(). While default constructors take no arguments, you still need need to provide a definition for them. If they do absolutely nothing, not even member initialization, then you could simply do what you did for your destructors: character() { } and player() { }.

However, you could (and you probably should), initialize the data members in the constructors, using initializer list syntax. For example, for the character class, it would be:

character() : hp(100), name("Mario") { }

Note that you don't need the semicolon after }. Or you could NOT use initializer lists and have:

character() {
    hp = 100;
    name = "Mario";
}