Signing in a new user with TwitterKit

When calling Twitter logInWithCompletion:, by default the user will be presented with a sheet with all of the Twitter accounts already registered at the system level (that is, in the ACAccountStore). Sometimes though, it’s handy to let the user add another Twitter account on the fly. Here’s how.

Use the web based authentication method

TwitterKit 2.0 added Twitter loginWithMethods:completion:. This method lets you explicitly choose how to prompt the user for authentication. By using the web based authentication only, you’ll show the user the Twitter login form in a web view, making it possible for the user to type in a new username.

Clear cookies between usages

If you try this, you’ll notice that subsequent calls to loginWithMethods:completion: don’t result in the desired behaviour. Specifically, the web view appears with the user already logged in to Twitter. The web view appears briefly and disappears, leaving the user logged in to whichever account she last used.

This effect can be eliminated by clearing the cookies stored in NSHTTPCookieStorage. Here’s a brute force example that deletes all cookies for the current app (as taken from http://stackoverflow.com/a/4471747/95869)

let storage = NSHTTPCookieStorage.sharedHTTPCookieStorage()
if storage.cookies != nil {
  for cookie in storage.cookies! {
    storage.deleteCookie(cookie)
  }
}
NSUserDefaults.standardUserDefaults().synchronize()