2. static #

Created Saturday 11 January 2020

Here, we’ll study about use of static w.r.t OOP in C++ . When we declare a member of a class as static it means no matter how many objects of the class are created, there is only one copy of the static member.

Static Data Members #

• A static member is shared by all objects of the class.
• They are not associated with any object, i.e they don’t occupy an objects memory.
• They are present even if no objects have been made. i.e they can be called/accessed using class_name::member even before any object is made.
• They can be const, i.e static const variables are possible.
• They had to be initialized outside the class(before C++11), using the scope resolution operator. i.e data_type class_name :: static_variable_name = value;. This was done to avoid duplicate initializations at place wherever the class header has been copied. The static data member may be a private one.
• But in C++11 we can initialize them inside, by using the inline modifier.

inline static int x = 2;

Complete vs Incomplete declaration.

• Changes can be made using the objects too, but should be avoided.
• A constructor can be used to keep track of number of objects created. This is an appilcation.

Static Member Functions #

• Static member functions can work only on static values and hence don’t need an object to be invoked(you can do so if you wish). They can be invoked using the class_name itself(if public).
• Static objects/functions don’t have access to ‘this’. But can create their own non-static objects if required. i.e They cannot make changes to the caller object.
• static member functions cannot be tagged const. Because const will need to generate a const T* = this, but this is inaccessible for static functions. Pretty useless too.
• C++ does not support static constructor.
• Static member functions can even be called without an object, like this:

MyClass::f(); // f is a static member function