Added Installation channel modification so that account holders can manually…

Added Installation channel modification so that account holders can manually add/remove subscriptions of users on their application

parse_rest/installation.py

@@ -19,6 +19,35 @@ from parse_rest.query import QueryManager
 class Installation(ParseResource):
     ENDPOINT_ROOT = '/'.join([API_ROOT, 'installations'])
 
+    @classmethod
+    def _get_installation_url(cls, installation_id):
+        """
+        Get the URL for RESTful operations on this particular installation
+        """
+        return '/'.join([cls.ENDPOINT_ROOT, installation_id])
+
+    @classmethod
+    def update_channels(cls, installation_id, channels_to_add=set(),
+                        channels_to_remove=set(), **kw):
+        """
+        Allow an application to manually subscribe or unsubscribe an
+        installation to a certain push channel in a unified operation.
+
+        this is based on:
+        https://www.parse.com/docs/rest#installations-updating
+
+        installation_id: the installation id you'd like to add a channel to
+        channels_to_add: the name of the channel you'd like to subscribe the user to
+        channels_to_remove: the name of the channel you'd like to unsubscribe the user from
+
+        """
+        installation_url = cls._get_installation_url(installation_id)
+        current_config = cls.GET(installation_url)
+
+        new_channels = list(set(current_config['channels']).union(channels_to_add).difference(channels_to_remove))
+
+        cls.PUT(installation_url, channels=new_channels)
+
 
 class Push(ParseResource):
     ENDPOINT_ROOT = '/'.join([API_ROOT, 'push'])