The Sorting Hat
The Sorting Hat sorts Firebase events into their Houses. It accomplishes this through what we shall call magic.
For muggles: This allows you to watch for new children added to a particular Firebase path and invoke a callback function.
var SortingHat = require('sortinghat'),
hat = new SortingHat(new Firebase('https://example.firebaseio.com'));
hat.watch('/foo', function(snap) {
console.log('new foo:', snap.val());
});
Methods
new SortingHat(firebase)
require('sortinghat')
gives you this constructor. Pass in a ready-to-use Firebase
object.
watch(path, [options,] [cb])
Watch path
for new children. In order to not download all the data under this path, Sorting Hat requires you to use a well-defined ordering of data. You cannot watch for children added at arbitrary locations; they must be added to the end of the order.
options.order
key
- Items will be added with keys having a monotonically increasing alpha order. Suitable for use withpush()
.priority
- Items will be added with a monotonically increasing priority.- anything else - Items will be objects containing this key, whose value will monotonically increase (ie a created timestamp).
trigger(path, [options,] [cb])
Watch path
for new children. There are no constraints on order, however this requires that the Sorting Hat downloads all data from path
.
When calling a Lambda function, the new child will be automatically deleted from Firebase after Lambda accepts the invocation.
WARNING! Only use trigger
on a path where you plan on deleting the children shortly after they are created. In other words, path
should usually be empty. If you ignore this advice, the Sorting Hat will use all your memory and/or crash.
responder(path, [options,] [cb])
Exactly like trigger
-- watches path
for new children with no constraints on order (and the associated caveats) -- except adds /request
to the supplied path
.
cb
The cb
argument to watch
, trigger
, and responder
can optionally take a callback function.
If you supply a function, it is invoked whenever there is a change. The one and only argument passed to the function is the Firebase Snapshot
of the new child.
watch
, trigger
, and responder
also return a FirebaseWatcher
. This object is an EventEmitter
that emits child_added
events for watch
and request
events for trigger
and responder
.