OAuth2Client is a free and open source OAuth2 library for Mac OS X and iOS developers (Cocoa and Cocoa touch).
The OAuth2Client library implements the native application profile and supports the end-user authorization endpoint via an internal or an external user-agent.
Furthermore, OAuth2Client also supports the user credentials flow by prompting the end-user for their username and password and use them directly to obtain an access token.
Detailed instructions on how to use the OAuth2Client framework within your own projects are available here.
· Apple Xcode