github/swift-style-guide — pull request #21 by dennda (2014-11-25 19:54:52+00:00)
Title: Propose never using implicitly unwrapped optionals.

This should be straightforward.

Implicitly unwrapped optionals are bad. IMHO they shouldn't exist in the language and are only a stopgap solution used by Apple while they migrate all AppKit/UIKit signatures over to explicit optionals (or no optionals).

I am not sure if this needs further explanation…?

The only place I have ever found implicitly unwrapped optionals to be somewhat OK is in conjunction with IBOutlets, but I don't know if that should be mentioned here. Thoughts?