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.
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:
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