To explore Apple’s documentation on Swift, start at developer.apple.com/swift. Here are two particular resources to look for. We suggest bookmarking them and visiting them when you want to review a particular concept or dig a little deeper.
This guide describes many features of Swift. It starts with the basics and includes example code and lots of detail. It also contains the language reference and formal grammar of Swift.
The standard library reference lays out the details of Swift types, protocols, and global, or free, functions.
(Apple also maintains documentation for the Cocoa frameworks, which you will ...