Callback URI invoked after successful or unsuccessful user authorization. A ‘code’ query string is appended if authentication is successful and an ‘error’ query string if it is not successful. Required.
OAuth 2.0 response type. Must be ‘code’. Required.
copy) NSString *state;
This parameter is preserved in the authorization flow and returned to the client as a query string parameter in the ‘redirect_uri’. The client may validate this in order to protect against a Cross Site Request Forgery (XSRF) attempt.