2. const member functions #

Created Saturday 11 January 2020

What is const in OOP? #

• A const object - an object whose data-members are all const. This is by definition.
• A const member function is a member function that guarantees it will not modify the object or call any non-const member functions (as they may modify the object).

How to make a function ‘const’ #

• If our const mark(on the function) is fake(i.e it changes the object), then the const binding of the data member will be give an error.
• How to tag a function as const. Put const after the parentheses, before the definition code block.

class A
{
	...
	void foo() const
	{
		// code
	}
	...
};

Note

1. Const functions can be invoked through both const and non const objects.
2. Const objects can access only const functions, i.e const objects are limited in their actions.
3. A const function can change attributes for a non-const param passed to it. The only restriction is changing the caller object.
4. Special functions(like constructors, destructor and copy assignment operator) cannot be made const.
5. A function can be overloaded to have a const function and a non-const, both are considered different, because constness is part of the function signature. Here a const object will call the const function, otherwise the normal function is called.

How does const work #

const functions just have a** const T* instead of a normal this. **

Changing a data structures in a const function #

Why use as constant functions?: https://en.wikibooks.org/wiki/C%2B%2B_Programming/Programming_Languages/C%2B%2B/Code/Keywords/return

• Remember const first takes value then tags the path constant.

https://stackoverflow.com