title: How to aggregate iOS push notifications using Parse
body: <p>so I'm developing an application where a user might get a notification based on some action but I only want the user to receive one notification of a specific type. An example might illustrate this better:</p>
  
  <p>Say a user on facebook makes a facebook post. If someone likes the post they'll get a notification. However, if 20 different people like that post I don't want 20 separate notifications when they finally check their phone. I want one notification that says '20 people have liked your post.' I also only want to track the new notifications. Say 20 people have liked your post. I don't want the notification for the next 5 who've liked your post to be '25 people have liked your post.' I want it to be '5 new people have liked your post.'</p>
  
  <p>What I don't know how to do is delete a notification that got sent using Parse. An idea I thought of off the top of my head for recording new posts was to keep track of what the user has seen for that post but that seems silly. It's a large amount of data to keep track of, compared to querying for a previous notification to that user for that channel (is that possible?).</p>
  
  <p>Anyways, I was hoping other users of Parse using push notifications might've faced this problem and how you all might've gotten around it. I would like to implement my own backend but I don't have the expertise and I'm currently focused on the client side. Any help or suggestion would be greatly appreciated. Thanks!</p>