Intro

Swift and iOS cheatsheet

Main links: Apple Documentation Swift 4

Optional

Unwrap

if way

@IBOutlet var messageLabel: UILabel?

if let messageLabel = messageLabel {
    messageLabel
}

Protocol

Simple

protocol MyProtocol {
//Protocol code here
}

Extension

extension MyProtocol {
//Extension code here
}

Extension constraints

only types that also conform to the MyAnotherProtocol protocol will receive the functionality defined in the extension

extension MyProtocol where Self: MyAnotherProtocol {
//Extension code here
}

Generics

Constraints

func fooFunction<T: MyClass, E: MyProtocol>(a: T, b: E) {
}