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.
Your homework is to browse through the Types section of the Swift Standard Library Reference and the sections of The Swift Programming Language guide on The Basics, Strings and Characters, and Collection Types. Solidify what you learned in this chapter and become familiar with the information these resources offer. If you know where to find the details when you need them, then you will feel less pressure to memorize them – letting you focus on iOS development instead.