Thread: object compostion

Dear Forum Members,
I am new to C++, and trying to learn object composition.

I have 2 classes: Point and Creature.
Point->int x and int y
Creature:-> Point location and string name

Below is my Point class header:

Code:

#ifndef POINT_H
#define POINT_H

class Point
{
    public:
        /** Default constructor */
        Point(int x, int y);

        Point();

        void set_x(int);
        void set_y(int);
        int get_x();
        int get_y();

    protected:

    private:
    int x;
    int y;
};

#endif // POINT_H

Below is my Point class cpp

Code:

#include "Point.h"

Point::Point(int t, int h)
{
    x=t;
    y=h;
    //ctor
}
void Point::set_x(int h){
    x=h;
}

void Point::set_y(int h){
    y=h;
}

int Point::get_x(){
    return x;
}

int Point::get_y(){
    return y;
}

My creature header file looks like:

Code:

#ifndef CREATURE_H
#define CREATURE_H
#include "Point.h"
#include <string>

class Creature
{
    public:
        /** Default constructor */
        Creature(Point &location, std::string name);
        /** Access loc
         * \return The current value of loc
         */
        Point Getloc() { return loc; }
        /** Set loc
         * \param val New value to set
         */
        void Setloc(Point &val) { loc = val; }
        /** Access name
         * \return The current value of name
         */
        std::string Getname() { return name; }
        /** Set name
         * \param val New value to set
         */
        void Setname(std::string val) { name = val; }
    protected:
    private:
        Point loc; //!< Member variable "loc"
        std::string name; //!< Member variable "name"
};

#endif // CREATURE_H

My creature cpp looks like this:

Code:

#include "Creature.h"
#include "Point.h"

Creature::Creature(Point &location, std::string n_name)
{
    //ctor

    name=n_name;
    loc=location;

}

I need to have a creature object with its location. The location will be passed as an object of Point.
I am getting error

undefined reference to 'Point::Point()'
at line:

Code:

Creature::Creature(Point &location, std::string n_name)

Default constructor was the issue? Why is it?
Edited the code and yes, it works. Thank you...

By constant and initialiser list, you mean: ?

Code:

Creature::Creature(const Point& location, std::string n_name)
:loc(location),name(n_name)

Originally Posted by laserlight

You forgot to define the default constructor for Point.

By the way, in the Creature constructor, the Point reference parameter should probably be a const reference instead. Likewise, the std::string paramater should be a const reference. Also, you should be using the initialiser list in the constructor to initialise the member variables.

Great!

Originally Posted by laserlight

Yes.