CODEWITHSUNDEEP
javascriptfirebase
iouhammi
iouhammi

Reputation: 1108

Unlink listener for parent does it applied to children in Firebase

I am using firebase to synch data in a real time app. After some treatment, I want to unlink all listeners added. So I put

myRef.off();

But I discover that some listeners are still attached.

My question is: when you put listeners to off for a parent node does it propagate to children or should I put off each level separately?

Upvotes: 5

Views: 2861

Answers (3)

Gene Bo
Gene Bo

Reputation: 12093

Thanks to the posts in this thread, I was able to figure out how stop my callbacks which kept firing after their initial invocation for the intended Firebase calls they were passed to. This unexpected callback was even happening when I updated directly in the console.

I got the following solution to disengage listeners once the callback runs:

var queryRef = someItemRef.limitToLast(1);

queryRef.on('child_added', function (data) {

    queryRef.off();
    onAddSomeItemReadyFunc(data);
});

For me - understanding the listener logic and avoiding "rogue callbacks" - has been a trickier aspect of working with Firebase DB. But we're gettn' there :)

@Frank van Puffelen, thank you yet again for good notes and examples to help us Firebase-client devs get back on track!

Upvotes: 0

Frank van Puffelen
Frank van Puffelen

Reputation: 599716

Let's try it.

ref.on("value", function(snapshot) { 
  console.log("parent: "+JSON.stringify(snapshot.val()));
});
ref.child("child").on("value", function(snapshot) { 
  console.log("child: "+JSON.stringify(snapshot.val()));
});
ref.set('1');
ref.child('child').set('2');
ref.off();
ref.child('child').set('3');
ref.child('child').off();
ref.set('4');

The output:

parent: "1"
child: "2"
parent: {"child":"2"}
child: "3"

So after calling off on the parent listener, the child listener still fires ("3"). But if we get the same child and call off, it doesn't for anymore ("4").

JSBin: http://jsbin.com/wutaza/edit?js,console

Conclusion: off() doesn't remove listeners from child nodes.

Upvotes: 8

André Kool
André Kool

Reputation: 4978

Detach a callback previously attached with on(). Note that if on() was called multiple times with the same eventType and callback, the callback will be called multiple times for each event, and off() must be called multiple times to remove the callback.

This comes from the firebase docs on the off() method (link).

So if i read this correct you have to call off() for every on() you did.

Upvotes: 1

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