What is the nil coalescing operator in swift?

Ans : 

Swift has very powerful in terms of safety because it has feature of optional.

Optional may be has value or may be not. So we try to assign some optional to any another string or any type, then it comes some problem.

Nil Coalescing operator is solution of above problem.

let myname : String = nil
let unwrappedname = myname ?? "Default"

It checks if myname is nill then Default will be assigned to unwrappedname.

So unwrappedname is type of String instead of String?.

Such way nil Coalescing operator ?? is very useful in Swift.