Refactor: Topic#invite_by_email

Extract Topic#email_already_existas_for? and Topic#grant_permission_to_user

app/models/topic.rb

@@ -426,11 +426,7 @@ class Topic < ActiveRecord::Base
       invite = Invite.create(invited_by: invited_by, email: lower_email)
       unless invite.valid?
 
-        # If the email already exists, grant permission to that user
-        if invite.email_already_exists and private_message?
-          user = User.where(email: lower_email).first
-          topic_allowed_users.create!(user_id: user.id)
-        end
+        grant_permission_to_user if email_already_exists_for?(invite)
 
         return
       end
@@ -444,6 +440,15 @@ class Topic < ActiveRecord::Base
     invite
   end
 
+  def email_already_exists_for?(invite)
+    invite.email_already_exists and private_message?
+  end
+
+  def grant_permission_to_user
+    User.where(email: lower_email).first
+    topic_allowed_users.create!(user_id: user.id)
+  end
+
   def max_post_number
     posts.maximum(:post_number).to_i
   end