Move mechanics of changeset subscriptions into the model

app/controllers/api/changesets_controller.rb

@@ -44,7 +44,7 @@ module Api
       cs.save_with_tags!
 
       # Subscribe user to changeset comments
-      cs.subscribers << current_user
+      cs.subscribe(current_user)
 
       render :plain => cs.id.to_s
     end
@@ -233,10 +233,10 @@ module Api
 
       # Find the changeset and check it is valid
       changeset = Changeset.find(id)
-      raise OSM::APIChangesetAlreadySubscribedError, changeset if changeset.subscribers.exists?(current_user.id)
+      raise OSM::APIChangesetAlreadySubscribedError, changeset if changeset.subscribed?(current_user)
 
       # Add the subscriber
-      changeset.subscribers << current_user
+      changeset.subscribe(current_user)
 
       # Return a copy of the updated changeset
       @changeset = changeset
@@ -259,10 +259,10 @@ module Api
 
       # Find the changeset and check it is valid
       changeset = Changeset.find(id)
-      raise OSM::APIChangesetNotSubscribedError, changeset unless changeset.subscribers.exists?(current_user.id)
+      raise OSM::APIChangesetNotSubscribedError, changeset unless changeset.subscribed?(current_user)
 
       # Remove the subscriber
-      changeset.subscribers.delete(current_user)
+      changeset.unsubscribe(current_user)
 
       # Return a copy of the updated changeset
       @changeset = changeset

app/models/changeset.rb

@@ -213,4 +213,16 @@ class Changeset < ApplicationRecord
 
     save_with_tags!
   end
+
+  def subscribe(user)
+    subscribers << user
+  end
+
+  def unsubscribe(user)
+    subscribers.delete(user)
+  end
+
+  def subscribed?(user)
+    subscribers.exists?(user.id)
+  end
 end

test/models/changeset_test.rb

@@ -71,4 +71,17 @@ class ChangesetTest < ActiveSupport::TestCase
       Changeset.from_xml(xml, :create => true)
     end
   end
+
+  def test_subscription
+    changeset = create(:changeset)
+    user = create(:user)
+
+    assert_not changeset.subscribed?(user)
+
+    changeset.subscribe(user)
+    assert changeset.subscribed?(user)
+
+    changeset.unsubscribe(changeset.subscribers.first)
+    assert_not changeset.subscribed?(user)
+  end
 end