Flip Flops
Part of being a good style guide is to keep up with the changes in Swift as they come. In this update of the style guide we tell you to do a couple of things exactly opposite of what we said in the past. Sorry. :]
For example, although the style guide still recommends using type inference rather than an explicit type annotation in most cases, initializing arrays an dictionaries is now different. The new preferred form is:
var names: [String] = []
var lookup: [String: Int] = [:]
Many publications, including Apple, now use this form. Even Swift engineer extraordinaire, Joe Groff was kind enough to chime in on this issue.
@rayfix That's my preference—makes var type clear, lets you write initial value in the same style as an expression with type context.
— Joe Groff (@jckarter) April 7, 2016
Another flip-flop is in the capitalization of enumerations. Following Apple’s lead, before we said to use UpperCamelCase. Now, in anticipation of the Swift 3 API Design Guidelines, lowerCamelCase is preferred. The rationale is that cases are values and should follow the same convention as other values. Since Xcode won’t fight you on the matter, we might as well adopting now. We welcome our new Optional .some and .none overlords when Swift 3 appears this Fall.
Where to Go From Here?
This style guide update contains a lot of smaller but important details not covered here: names of generic types, chaining closures, defining constants and more. Over time, you will see our tutorials and books adopt this style.
We encourage you to read through the entire guide as it is not that long. If there is something you like (or don’t), let us know in the comments below.
If you want to get even more involved, open a Github issue and start a community discussion on a specific issue. You can even create a pull request. Typos and errors that need to be immediately fixed will go directly into the master branch after a brief review period. A swift3 branch will handle changes for a future update this Fall.
Herb Sutter and Andrei Alexandrescu famously admonish:
"Think. Do follow good guidelines conscientiously; but don’t follow them blindly."
This is great advice; no set of programming guidelines can cover every use case. Exceptions will always exist. In addition to helping you read our code, we hope that this style guide helps authors worry less about the mundane and focus on more interesting things. Enjoy!
