Use projection for meteor publish subscribe - meteor

Question

I have a UI element framework, that works only with specific data model ( expects an object with "text" key). This is different from the data model that exists in my mongodb.
So my first idea was to use a projection and publish it to the listeners.
var db = MongoInternals.defaultRemoteCollectionDriver().mongo.db;
db.Element.aggregate({$project: { _id:1, text:"$description"}});
The Problem is that this is not a cursor, but just simple ejson object. What strategy should i use to give the UI framework needed data and to have a reactivity/data binding from both sides.

Answer 1

In your publication, instead of returning a cursor, you can use the lower level publish api to have finer control over the results.
For instance, when you return a cursor from a publication, Meteor calls the _publishCursor function which looks like this:
Mongo.Collection._publishCursor = function (cursor, sub, collection) {
var observeHandle = cursor.observeChanges({
added: function (id, fields) {
sub.added(collection, id, fields);
},
changed: function (id, fields) {
sub.changed(collection, id, fields);
},
removed: function (id) {
sub.removed(collection, id);
}
});
// We don't call sub.ready() here: it gets called in livedata_server, after
// possibly calling _publishCursor on multiple returned cursors.
// register stop callback (expects lambda w/ no args).
sub.onStop(function () {observeHandle.stop();});
// return the observeHandle in case it needs to be stopped early
return observeHandle;
};
So, you can modify your publication, to basically do the same thing, but also publish a text field, which gets its value from the description field, like so:
Given the following collection:
MyCollection = new Mongo.Collection("my_collection");
Your publish function might look like this:
Meteor.publish("myPub", function () {
var sub = this;
var observeHandle = myCollection.find().observeChanges({
added: function (id, fields) {
fields.text = fields.description; // assign text value here
sub.added("my_collection", id, fields);
},
changed: function (id, fields) {
fields.text = fields.description; // assign text value here
sub.changed("my_collection", id, fields);
},
removed: function (id) {
sub.removed("my_collection", id);
}
});
sub.ready()
// register stop callback (expects lambda w/ no args).
sub.onStop(function () {observeHandle.stop();});
};