WWDC23 SALE: Save 50% on all my Swift books and bundles! >>

Verbs and nouns

Available from Swift 3.0

Paul Hudson      @twostraws

This is the part where some people will start to drift off in confusion, which is a shame because it's important.

Here's are some quotes from the Swift API guidelines:

  • "When the operation is naturally described by a verb, use the verb’s imperative for the mutating method and apply the “ed” or “ing” suffix to name its nonmutating counterpart"
  • "Prefer to name the nonmutating variant using the verb’s past participle"
  • "When adding “ed” is not grammatical because the verb has a direct object, name the nonmutating variant using the verb’s present participle"
  • "When the operation is naturally described by a noun, use the noun for the nonmutating method and apply the “form” prefix to name its mutating counterpart"

Got that? It's no surprise that Swift's rules are expressed using lingustic terminology – it is after all a language! – but this at least gives me a chance to feel smug that I did a second degree in English. What it means is that many methods are changing names in subtle and sometimes confusing ways.

Let's start with a couple of simple examples:

myArray.enumerate()
myArray.enumerated()

myArray.reverse()
myArray.reversed()

Each time Swift 3 modifies the method by adding a "d" to the end: this is a value that's being returned.

These rules are mostly innocent enough, but it causes confusion when it comes to array sorting. Swift 2.2 used sort() to return a sorted array, and sortInPlace() to sort an array in place. In Swift 3.0, sort() is renamed to sorted() (following the examples above), and sortInPlace() is renamed to sort().

TL;DR: This means you need to be careful because in Swift 2.2 sort() returned a sorted array, but in Swift 3.0 sort() sorts the array in place.

Save 50% in my WWDC23 sale.

SAVE 50% To celebrate WWDC23, all our books and bundles are half price, so you can take your Swift knowledge further without spending big! Get the Swift Power Pack to build your iOS career faster, get the Swift Platform Pack to builds apps for macOS, watchOS, and beyond, or get the Swift Plus Pack to learn advanced design patterns, testing skills, and more.

Save 50% on all our books and bundles!

Other changes in Swift 3.0…

Download all Swift 3.0 changes as a playground Link to Swift 3.0 changes

Browse changes in all Swift versions

 
Unknown user

You are not logged in

Log in or create account
 

Link copied to your pasteboard.