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C++ class-object?

In C++, How one can restrict a class so tht it can have oly one object?

You can't, really. But you can, effectively. The question you need to ask is "What do I want to see happen when the code attempts to create a second instance?".

Still, this situation does arise often enough and is usually handled through the use of static class variables. For more information do a google search on "c++ singleton pattern".

What you want is known as a singleton and in a singleton class the constructor is private.
Instead you have a public static member function that returns a dynamically allocated instance
of the class and this instance is a static data member of the class itself.

Code:

class mysingleton

{

public:

  static mysingleton* get_instance()

  {

      if(!instance)

        instance = new mysingleton(/*arguments*/);

      return instance;

  }

private:

  mysingleton(/*arguments*/);

  static mysingleton *instance;

};



mysingleton* mysingleton::instance=NULL;

Use google to search for singleton (pattern) to learn more.