Enums and classes - Run time error !!

My aim before writing this code was to just practice and learn more about C++ .

The code consists of a class ball which has a ball's properties like colour , size , weight and also the 'brand' and price of the ball .

#include<iostream>
#include<string>
using namespace std;

class ball
{
private:
    int price;                                       //Price of a ball in rupees .
    enum colour { red , green , blue } colour;       // Colour of the ball .
    string brand;                                    // Brand of the ball REEBOK ADIDAS etcetera .
    float size;                                      // Diameter of the ball .
    enum weight { light , medium , heavy }weight;    // Qualitative weight .
public:  

    ball();
    void get_price();
    void get_colour();
    void get_brand();
    void get_size();
    void get_weight();
};
开发者_如何学C
ball::ball() : price(0) , brand(NULL) , size(0.0)
{
    cout<<"In the constructor";
    colour=blue;
    weight=medium;
}

void ball::get_price()
{
    cout<<"In the function get_price()"<<endl<<price<<endl;
}

void ball::get_colour()
{
    cout<<"In the function get_colour()"<<endl<<colour<<endl;
}

void ball::get_brand()
{
    cout<<"In the function get_brand()"<<endl<<brand<<endl;
}

void ball::get_size()
{
    cout<<"In the function get_size()"<<endl<<size<<endl;
}

void ball::get_weight()
{
    cout<<"In the function get_weight()"<<endl<<weight<<endl;
}

int main()
{
    ball glace;
    glace.get_price();
    glace.get_colour();
    glace.get_brand();
    glace.get_size();
    glace.get_weight();
}

The problem came with the usage of enums in class definition . Initially I got errors like C2436 , C2275 , C2064 . All the errors at each compilation were due to the enum . After fixing them , finally the above code is compilation error free ! But it's giving me a run-time error . !!

Can anyone explain it to me why ?

PS : I use Microsoft Visual C++ 2005 express edition .

You call brand(NULL) on a std::string, that's the runtime error you are getting. It's calling the std::string constructor that takes a char const*, to create from a C string, and it can't be NULL. To construct an empty std::string simply call brand() in your initialization list, or even skip it since if you do the default constructor would be called automatically by the compiler.