Descriptive and consistent naming makes software easier to read and understand. We use the Swift naming conventions described in the API Design Guidelines. We find Ray Wenderlich swift style guidelines valuable, below are some of his main takeaways that we incorporate into our work.
Prose
When referring to methods in prose, being unambiguous is critical. To refer to a method name, use the simplest form possible.
For the above example using UIGestureRecognizer, 1 is unambiguous and preferred.
Pro Tip: You can use Xcode's jump bar to lookup methods with argument labels.
Class Prefixes
Swift types are automatically name spaced by the module that contains them and you should not add a class prefix such as RW. If two names from different modules collide you can disambiguate by prefixing the type name with the module name. However, only specify the module name when there is possibility for confusion which should be rare.
import SomeModule
let myClass = MyModule.UsefulClass()
Delegates
When creating custom delegate methods, an unnamed first parameter should be the delegate source. (UIKit contains numerous examples of this.)
Preferred:
func namePickerView(_ namePickerView: NamePickerView, didSelectName name: String)
func namePickerViewShouldReload(_ namePickerView: NamePickerView) -> Bool
Not Preferred:
func didSelectName(namePicker: NamePickerViewController, name: String)
func namePickerShouldReload() -> Bool
Use Type Inferred Context
Use compiler inferred context to write shorter, clear code. (Also see Type Inference.)
Preferred:
let selector = #selector(viewDidLoad)
view.backgroundColor = .red
let toView = context.view(forKey: .to)
let view = UIView(frame: .zero)
Not Preferred:
let selector = #selector(ViewController.viewDidLoad)
view.backgroundColor = UIColor.red
let toView = context.view(forKey: UITransitionContextViewKey.to)
let view = UIView(frame: CGRect.zero)
Generics
Generic type parameters should be descriptive, upper camel case names. When a type name doesn't have a meaningful relationship or role, use a traditional single uppercase letter such as T, U, or V.
Preferred:
struct Stack<Element> { ... }
func write<Target: OutputStream>(to target: inout Target)
func swap<T>(_ a: inout T, _ b: inout T)
Not Preferred:
struct Stack<T> { ... }
func write<target: OutputStream>(to target: inout target)
func swap<Thing>(_ a: inout Thing, _ b: inout Thing)
Language
Use US English spelling to match Apple's API.
Preferred:
let color = "red"
Not Preferred:
let colour = "red"