Functional Programming: A PragPub Anthology

Fancy Parameters

Compared to Objective-C, Swift has a lot of extra options for what type of parameters can be passed in. Here are some examples.

Optional Parameter Types

In Swift, there is a new concept of optional types:

Optionals say either “there is a value, and it equals x” or “there isn’t a value at all.” Optionals are similar to using nil with pointers in Objective-C, but they work for any type, not just classes. Optionals are safer and more expressive than nil pointers in Objective-C and are at the heart of many of Swift’s most powerful features.

To indicate that a parameter type is optional (can be nil), just add a question mark after the type specification:

func myFuncWithOptionalType(parameter: String?) {
 // function execution ...