Swift Optional Type

An introduction to optionals

The Swift optional data type is a relatively new concept that does not exist in most other programming languages.

The purpose of the optional type is to provide a safe and consistent approach to handling situations where a variable or constant may not have any value assigned to it.

Declaring an optional variable

Variables are declared as being optional by placing a ? character after the type declaration. The following code declares an optional Int variable named index:

var index: Int?

The variable index can now either have an integer value assigned to it or have nothing assigned to it.

Note: Behind the scenes, and as far as the compiler and runtime are concerned, an optional with no value assigned to it actually has a value of nil.

An optional can easily be tested (typically using an if statement) to identify whether it has a value assigned to it as follows: