Terribly simple OS X Swift App to demonstrate use of the Swift OAuth2 Framework against the GitHub API. It lets you login to GitHub and then pulls your user information, displaying your avatar and full name (for some reason the avatar doesn't automatically center; resize the window for that to happen).
Take a look at the GitHubLoader class, which is intended to be used as a singleton and handles the OAuth flow as well as requests to the GitHub API.
There also is an iOS Sample App which uses Cocoapods to integrate the OAuth2 framework.
Do a recursive checkout, then open the project in Xcode and run it:
$ git clone --recursive https://github.com/p2/OAuth2App.git
I have waived all copyright and related or neighboring rights to OAuth2App.