Swift Programming for Mobile App Development/

...

/

Swift Optional Type

Swift Optional Type

Explore the use of the Swift optional data type to write more reliable code and learn how this works to save you hours of debugging time.

We'll cover the following...

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:

Press + to interact
var index: Int?
if index != nil {
    print("index variable has a value assigned to it")
} else {
    print("index variable has no value assigned to it")
}

Forced unwrapping

If an optional has a value assigned to it, that value is said to be wrapped within the optional. The value wrapped in an optional may be accessed using a concept referred to as forced unwrapping. This simply means that the underlying value is extracted from the optional data type which is a procedure that is ...