C++ class inheritance variables

Question

I'm working on a game, and I want to store the character belongs to a unit inside the class that defines the units. (as objects)

This is the defining class. (I use inheritance)

class Units
{
    public:
       char indicator;

        Units();
        virtual ~Units();
    protected:
    private:
};

Units::Units (){}
Units::~Units (){}


class WoodenBoxClass: public Units
{
    public:
        WoodenBoxClass.indicator = 'B';
};

During the compilation, when "WoodenBoxClass.indicator = 'B';" comes, I get an error message:

50|error: expected unqualified-id before '.' token

What should I do? The main question is that how can I reach that the "indicator" variable is the same to every "WoodenBoxClass" object?

Answer 1

You need to initialize member variables in the class constructor. There are two ways to do it:

1. Simply assign to it in the child-class constructor

   WoodenBoxClass()
   {
       indicator = 'B';
   }
   

2. Have a constructor in the base class that takes the indicator as argument, and use an initializer list in the child-class constructor:

   class Unit
   {
       ...
       explicit Unit(char ind) : indicator(ind) {}
       ...
   };
   
   class WoodenBoxClass : public Unit
   {
       ...
       WoodenBoxClass() : Unit('B') {}
       ...
   };
   

Answer 2

To keep the "indicator" variable same to every "WoodenBoxClass" object, you can use static variable.

class WoodenBoxClass: public Units
{
    public:
        static char indicator = 'B';
};

class Units
{
    public:
       //char indicator;   //not necessary actually

        Units();
        virtual ~Units();
    protected:
    private:
};