Optional Binding

Optional binding allows getting the value inside an optional. It is a variant of the if-statement.

If the optional contains a value, the first branch is executed and a temporary constant or variable is declared and set to the value contained in the optional; otherwise, the else branch (if any) is executed.

Optional bindings are declared using the if keyword like an if-statement, but instead of the boolean test value, it is followed by the let or var keywords, to either introduce a constant or variable, followed by a name, the equal sign (=), and the optional value.

let maybeNumber: Int? = 1

if let number = maybeNumber {
    // This branch is executed as `maybeNumber` is not `nil`.
    // The constant `number` is `1` and has type `Int`.
} else {
    // This branch is *not* executed as `maybeNumber` is not `nil`
}

let noNumber: Int? = nil

if let number = noNumber {
    // This branch is *not* executed as `noNumber` is `nil`.
} else {
    // This branch is executed as `noNumber` is `nil`.
    // The constant `number` is *not* available.
}