1. const fields - Intialization List #

Created Saturday 11 January 2020

• How do we work with const data members? If we don’t initialize, then the value is stuck and will be the same for all objects.

• C++ does not allow initialization outside a function.

To solve this problem, we need to use initialization lists.

Syntax

class A{
	int a, b;
	const string c;
	int d[4];
	...
	void f() : a(2), b(a), c("Sanjar"), d{1,2,3,4} // intialization list
	{
		...
	}
	...
};

• We can initialize any data member using i-lists
• It is the first thing that is run, when an object is being created.
• Variables in the i-list are not initialized in the order that they are specified in the i-list. Instead, they are initialized in the order in which they are declared in the class.
• Making a constructor(with initialization list) is a must if at least one data member is const or reference.
• We should not write ‘this’ in the initialization list, except for a reference variable. That would give an error. The names are not overshadowed here.

Use case:

1. If we want a const data member.
2. If our class has reference data members. (Both need to be declarized).

• In C++11 and higher, we can initialize const and references just outside the constructor too.
• Even here, the initialization list is evaluated first.