C++ static Class Members

   Rather than defining a generally accessible global object,a class can define a class static member.

Oridinary,nonstatic data members exist in each object of the class type.Unlike ordinary date members,a static data member exists independently of any object of its class;each static data member is an object associated with the class,not with the objects of that class.

   A static member function has no this parameter.It may directly access the static members of its class but may not directly use the nonstatic members.

Defining static members :

class Account { public: void applyint() { amount += amount*stcRate; } static double rate() { return stcRate; } static void rate(double); //sets a new rate provate: std::string owner; double amount; static double stcRate; static double initRate(); };

Using a Class static member

A ststic member can be invoked directly from the class using the scope operator or indirectly through an object,reference,or pointer to an object of its class type.

Account ac1; Account *ac2 = &ac1; double rate; rate = ac1.rate(); //through an Account object or reference rate = ac2->rate(); //through a pointer to an Account object rate = Account::rate(); //directly from the class using the scope operator

static Member Functions

When we define a static member outside the class,we do not respecify the static keyword.The keyword appers only with the declaration inside the class body:

//static Functions have no this pointer //static member is not part of any object //static member functions may not declared as const //static member functions may also not to be declared as virtual void Account::rate(double newRate) { stcRate = newRate; }

static Data Members

static data members must be defined (exactly once)outside the class body.static members are not initialized through te constructor(s) and instead should be initilaized when they are defined.

//define and initialize static class member double Account::stxRate = initRate();