Merge pull request #3830 from PoqXert/master

iOS GameCenter: Add authenticate method

tutorials/platform/services_for_ios.rst

@@ -176,8 +176,9 @@ Game Center
 Implemented in ``platform/iphone/game_center.mm``.
 
 The Game Center API is available through the "GameCenter" singleton. It
-has 8 methods:
+has 9 methods:
 
+-  ``Error authenticate();``
 -  ``bool is_authenticated();``
 -  ``Error post_score(Variant p_score);``
 -  ``Error award_achievement(Variant p_params);``
@@ -189,6 +190,37 @@ has 8 methods:
 
 plus the standard pending event interface.
 
+authenticate
+~~~~~~~~~~~~
+
+Authenticates a user in Game Center.
+
+Response event
+^^^^^^^^^^^^^^
+
+The response event will be a dictionary with the following fields:
+
+On error:
+
+::
+
+    {
+      "type": "authentication",
+      "result": "error",
+      "error_code": the value from NSError::code,
+      "error_description": the value from NSError::localizedDescription,
+    }
+
+On success:
+
+::
+
+    {
+      "type": "authentication",
+      "result": "ok",
+      "player_id": the value from GKLocalPlayer::playerID,
+    }
+
 post_score
 ~~~~~~~~~~