CODEWITHSUNDEEP
javascriptangularfirebasefirebase-realtime-database
Simon
Simon

Reputation: 2538

Firebase - child_added being called on delete of item

I have a list of post's and I'm fetching them with .on('child_added') the problem is that I only want to get the post's when an item is added and not when it is removed, however, it seems that .on('child_added') gets called even when a post is removed. Which is not what I need in my case.

Here is my function:

if(fromClick) { this.subscription.off(); this.firstRun = true;}
this.postFeed = new Array();
this.subscription = this.database.database.ref('/posts/'+this.locationId)
   .orderByChild('created')
   .limitToLast(10);

this.subscription.on('child_added', (snapshot) => {
   this.postFeed.push(snapshot.val());
});

So it displays last 10 and then when an item is added it adds that to the array as well, but when an item is removed it gets called again..

How can I prevent this? So that the call only happens for post's that are added?

Upvotes: 1

Views: 276

Answers (1)

Frank van Puffelen
Frank van Puffelen

Reputation: 599716

If you're calling:

this.database.database.ref('/posts/'+this.locationId)
   .orderByChild('created')
   .limitToLast(10);

You are creating a query that contains the 10 most recent posts. If you remove one of those, another one becomes the 10th most recent posts, so you get a child_added for that.

The only thing I can imagine is only getting the 10 once, and then doing a limitToLast(1):

this.database.database.ref('/posts/'+this.locationId)
   .orderByChild('created')
   .limitToLast(10)
   .once("value", function(snapshot) {
     snapshot.forEach(function(child) {       
       // These are the initial 10 children
     });
   });
this.database.database.ref('/posts/'+this.locationId)
   .orderByChild('created')
   .limitToLast(1)
   .on("child_added", function(snapshot) {
     // This is the latest child, but this will also fire when you remove the current latest
   });

Upvotes: 1

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