AppAuth for iOS and macOS is a client SDK for communicating with OAuth 2.0 and OpenID Connect providers. It strives to directly map the requests and responses of those specifications, while following the idiomatic style of the implementation language. In addition to mapping the raw protocol flows, convenience methods are available to assist with common tasks like performing an action with fresh tokens.
The Google Sign-In SDK allows users to sign in with their Google account from third-party apps.
GTMAppAuth enables you to use AppAuth with the Google Toolbox for Mac - Session Fetcher and Google APIs Client Library for Objective-C For REST libraries by providing an implementation of GTMFetcherAuthorizationProtocol for authorizing requests with AppAuth.