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Knockout component updating observable not being subscribed to by parent view model?

I've written a component called Upload which allows users to upload files and then report back with a JSON object with these files. In this particular instance, the Upload component has a parameter which comes from a parent view model:
<upload params="dropzoneId: 'uploadFilesDropzone', postLocation: '/create/upload', uploadedFiles: uploadedFiles"></upload>
The one of importance is called uploadedFiles. The parameter binding here means I can reference params.uploadedFiles on my component and .push() new objects onto it as they get uploaded. The data being passed, also called uploadedFiles, is an observableArray on my parent view model:
var UploadViewModel = function () {
// Files ready to be submitted to the queue.
self.uploadedFiles = ko.observableArray([]);
};
I can indeed confirm that on my component, params.uploadedFiles is an observableArray, as it has a push method. After altering this value on the component, I can console.log() it to see that it has actually changed:
params.uploadedFiles.push(object);
console.log(params.uploadedFiles().length); // was 0, now returns 1
The problem is that this change does not seem to be reflected on my parent viewmodel. self.uploadedFiles() does not change and still reports a length of 0.
No matter if I add a self.uploadedFiles.subscribe(function(newValue) {}); subscription in my parent viewmodel.
No matter if I also add a params.uploadedFiles.valueHasMutated() method onto my component after the change.
How can I get the changes from my array on my component to be reflected in the array on my parent view model?

Why do you create a new observable array when the source already is one? You can't expect a new object to have the same reference as another one: simply pass it to your component viewModel as this.uploads = params.uploads. In the below trimmed-down version of your example, you'll see upon clicking the Add button that both arrays (well the same array referenced in different contexts) stay in sync.
ko.components.register('upload', {
viewModel: function(params) {
this.uploads = params.uploads;
this.addUpload = function() { this.uploads.push('item'); }.bind(this);
},
template: [
'<div><button type="button" data-bind="click: addUpload">Add upload</button>',
'<span data-bind="text: uploads().length + \' - \' + $root.uploads().length"></span></div>'].join('')
});
var app = {
uploads: ko.observableArray([])
};
ko.applyBindings(app);
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.2.0/knockout-min.js"></script>
<div data-bind="component: {name: 'upload', params: {uploads: uploads}}"></div>
It is only in case your source array is not observable that things get a little more complicated and you need to have a manual subscription to update the source, eg. you would insert the following in the viewModel:
this.uploads.subscribe(function(newValue) { params.uploads = newValue; });
Additionally the output in the text binding would not be updated for the source because it is not observable. If for some reason that I cannot conceive of you would want to have 2 different observableArrays (1 source & 1 component), you should still be able to do with the line above, but replace the function code with params.uploads(newValue)

The problem may be related to this bug (to be confirmed): https://github.com/knockout/knockout/issues/1863
Edit 1: So this was not a bug. You have to unwrap the raw param to access the original observable. In your case, it would be:
params.$raw.uploadedFiles() //this would give you access to the original observableArray and from there, you can "push", "remove", etc.
The problem is that when you pass a param to a component, it gets wrapped in a computed observable and when you unwrap it, you don't have the original observableArray.
Reference: http://knockoutjs.com/documentation/component-custom-elements.html#advanced-accessing-raw-parameters

While Binding Property that involves Parent --> Child Relation
Use Binding in this way
If You want to bind data to Child Property
data-bind='BindingName : ParentViewmodel.ChildViewModel.ObservableProperty'
Here it seems you want to subscibe to a function when any data is pushed in Array for that you can write subscribe on Length of Observable array which can help you capture event that you want.
This should solve your problem.

Computed vs Observes on Controller in Ember

It was always my understanding that .observes('someProperty') and .property('someProperty') worked exactly the same, except that the former is used for triggering function calls and the latter is used to keep object properties up to date.
But now I'm having a problem. My controller code looks like this:
_logChange: function(){
console.log('model array observer fired');
}.observes('model.#each'),
statsData: function(){
console.log('statsData being updated');
...
return someArray;
}.property('model.#each')
The observer and computed property both watch model.#each but for some reason, the observer fires on every model change and the property only updates TWICE before mysteriously going dead. statsData is calculated once on initial page load, and once on the first route transition, then after that, none of the transitions (with the changes in the underlying model they make) affect it.
What's going on here? Shouldn't they respond to change in the same way?
Note that I am using the statsData property in my template.

observers fire immediately, computed's fire as part of the run loop and scheduled in a debounced fashion. Currently all you're watching is that you add or remove an item to the collection, not whether or not a property on one of the items in the collection has changed. If you want to watch a particular property, you need to specify it.
statsData: function(){
console.log('statsData being updated');
...
return someArray;
}.property('model.#each.cost')
if you just want to watch the collection changing you should just use []
statsData: function(){
console.log('statsData being updated');
...
return someArray;
}.property('model.[]')

Thanks to the lovely folks on Ember IRC, I was able to figure it out. The problem was that I was passing statsData to a component, like this: {{common-statistics values=statsData}} and in the component, I had this function:
_validateValues: function(){
var values = this.get('values');
if(!values || !Ember.isArray(values) || values.length === 0)
{
this.set('values',[]);
}
}.on('willInsertElement')
which is, as you can see, setting values if it's not what the component is expecting. Unfortunately, this was affecting statsData on the controller as well, thanks to this JavaScript language feature. By setting statsData in the component, I was breaking the computed property on the controller.
So it was never a problem with Ember at all. I just failed to realize that object properties on Ember objects behave the same way they do on "regular JavaScript objects."

Difficulty accessing actual objects in "didInsertElement" code in Ember

I'm having a repeated problem with accessing elements, specifically elements obtained via reference from another element, in Ember. I have javascript running in a "didInsertElement" hook in the view, which is what most places on the web seem to indicate is the correct place to be running that logic.
However, the ember object I'm trying to access isn't real - Ember (presumably EmberData) is returning a blank placeholder object that doesn't have any of the required values. Every attribute is undefined.
I've tried waiting for the promise to resolve... but it's not a promise, it's just a fake object with undefined attributes. I've tried using Ember.run.next, to insure things finished loading first. Neither of these two solutions, or any of the others I've tried, have worked.
Here's an example of what I mean:
template:
{{#each entry in list.entries}}
{{display-note note=entry}}
{{/each}}
component:
didInsertElement: function(){
alert(this.get("note").get("title"));
}
This inconsistently returns "undefined", even more inconsistently in situations where I'm passing a list of objects (something like {{display-notes notes=list.entries}} ).
Doing things like {{list.entry.title}} in the template works fine, though - the data is loading, it's just that it's being replaced by a "fake object" until that happens, and I don't know how to tell the ember app to wait until it's real to run my code and try and access it.
This is especially true for self references. Sometimes, rarely, the above code seems to work - but if I have a tree of, say, comments, which hasMany comments as children, attempting to access children fails even in the template. This might be due to another problem, though, or a combination of the two issues.

I'm guessing that note is undefined here:
didInsertElement: function(){
alert(note.get("title"));
}
With didInsertElement, start from the current view (i.e. this) and get your data from there. Assuming you are in the NoteView it would look like this:
App.NoteView = Ember.View.extend({
title : 'hello world'
didInsertElement: function (){
alert(this.get('title'));
}
})

Passing object available in the template into the {{render}} helper doesn't seem to work

I have an object defined globally as App.configObj which contains a property data. Inside a view's template I can use {{App.configObj.data}} to display the value and it works fine.
Inside that same template, I use {{render "viewC" model config=App.configObj}} to render a similar view, but the config property on that view remains null on didInsertElement. Other arguments set to primitive values are correctly set at that point.
Since App.configObj is definitely available in that context, shouldn't I be able to pass it into that view?
Here is the jsbin that illustrates the situation: http://emberjs.jsbin.com/misiyaki/12/edit
If you comment out the render call for ViewC, you can see that {{App.configObj.data}} renders just fine in the template.
My goal is to use an object encapsulating several properties to configure the view, so I need to be able to pass that object in. I spent a lot of time searching for similar content online but didn't find anyone trying this.
What am I missing?
Thanks!

I understand your struggle here with not being able to pass in a property in your render code... but in this case it doesn't seem that that is truly necessary.
Here is a fiddle with some changes to show you another way, that is essentially the same thing if i understood your intentions correctly. http://emberjs.jsbin.com/misiyaki/15/edit
The new code for your view:
App.ViewCView = Em.View.extend({
name: 'testName',
config: function () {
return App.configObj;
}.property(),
data: function () {
return this.get('config.data')
}.property('config'),
templateName: 'view-c'
});
Hope this helps!

How to clear/remove observable bindings in Knockout.js?

I'm building functionality onto a webpage which the user can perform multiple times. Through the user's action, an object/model is created and applied to HTML using ko.applyBindings().
The data-bound HTML is created through jQuery templates.
So far so good.
When I repeat this step by creating a second object/model and call ko.applyBindings() I encounter two problems:
The markup shows the previous object/model as well as the new object/model.
A javascript error occurs relating to one of the properties in the object/model, although it's still rendered in the markup.
To get around this problem, after the first pass I call jQuery's .empty() to remove the templated HTML which contains all the data-bind attributes, so that it's no longer in the DOM. When the user starts the process for the second pass the data-bound HTML is re-added to the DOM.
But like I said, when the HTML is re-added to the DOM and re-bound to the new object/model, it still includes data from the the first object/model, and I still get the JS error which doesn't occur during the first pass.
The conclusion appears to be that Knockout is holding on to these bound properties, even though the markup is removed from the DOM.
So what I'm looking for is a means of removing these bound properties from Knockout; telling knockout that there is no longer an observable model. Is there a way to do this?
EDIT
The basic process is that the user uploads a file; the server then responds with a JSON object, the data-bound HTML is added to the DOM, then the JSON object model is bound to this HTML using
mn.AccountCreationModel = new AccountViewModel(jsonData.Account);
ko.applyBindings(mn.AccountCreationModel);
Once the user has made some selections on the model, the same object is posted back to the server, the data-bound HTML is removed from then DOM, and I then have the following JS
mn.AccountCreationModel = null;
When the user wishes to do this once more, all these steps are repeated.
I'm afraid the code is too 'involved' to do a jsFiddle demo.

Have you tried calling knockout's clean node method on your DOM element to dispose of the in memory bound objects?
var element = $('#elementId')[0];
ko.cleanNode(element);
Then applying the knockout bindings again on just that element with your new view models would update your view binding.

For a project I'm working on, I wrote a simple ko.unapplyBindings function that accepts a jQuery node and the remove boolean. It first unbinds all jQuery events as ko.cleanNode method doesn't take care of that. I've tested for memory leaks, and it appears to work just fine.
ko.unapplyBindings = function ($node, remove) {
// unbind events
$node.find("*").each(function () {
$(this).unbind();
});
// Remove KO subscriptions and references
if (remove) {
ko.removeNode($node[0]);
} else {
ko.cleanNode($node[0]);
}
};

You could try using the with binding that knockout offers:
http://knockoutjs.com/documentation/with-binding.html
The idea is to use apply bindings once, and whenever your data changes, just update your model.
Lets say you have a top level view model storeViewModel, your cart represented by cartViewModel,
and a list of items in that cart - say cartItemsViewModel.
You would bind the top level model - the storeViewModel to the whole page. Then, you could separate the parts of your page that are responsible for cart or cart items.
Lets assume that the cartItemsViewModel has the following structure:
var actualCartItemsModel = { CartItems: [
{ ItemName: "FirstItem", Price: 12 },
{ ItemName: "SecondItem", Price: 10 }
] }
The cartItemsViewModel can be empty at the beginning.
The steps would look like this:
Define bindings in html. Separate the cartItemsViewModel binding.
<div data-bind="with: cartItemsViewModel">
<div data-bind="foreach: CartItems">
<span data-bind="text: ItemName"></span>
<span data-bind="text: Price"></span>
</div>
</div>
The store model comes from your server (or is created in any other way).
var storeViewModel = ko.mapping.fromJS(modelFromServer)
Define empty models on your top level view model. Then a structure of that model can be updated with
actual data.
storeViewModel.cartItemsViewModel = ko.observable();
storeViewModel.cartViewModel = ko.observable();
Bind the top level view model.
ko.applyBindings(storeViewModel);
When the cartItemsViewModel object is available then assign it to the previously defined placeholder.
storeViewModel.cartItemsViewModel(actualCartItemsModel);
If you would like to clear the cart items:
storeViewModel.cartItemsViewModel(null);
Knockout will take care of html - i.e. it will appear when model is not empty and the contents of div (the one with the "with binding") will disappear.

I have to call ko.applyBinding each time search button click, and filtered data is return from server, and in this case following work for me without using ko.cleanNode.
I experienced, if we replace foreach with template then it should work fine in case of collections/observableArray.
You may find this scenario useful.
<ul data-bind="template: { name: 'template', foreach: Events }"></ul>
<script id="template" type="text/html">
<li><span data-bind="text: Name"></span></li>
</script>

Instead of using KO's internal functions and dealing with JQuery's blanket event handler removal, a much better idea is using with or template bindings. When you do this, ko re-creates that part of DOM and so it automatically gets cleaned. This is also recommended way, see here: https://stackoverflow.com/a/15069509/207661.

I think it might be better to keep the binding the entire time, and simply update the data associated with it. I ran into this issue, and found that just calling using the .resetAll() method on the array in which I was keeping my data was the most effective way to do this.
Basically you can start with some global var which contains data to be rendered via the ViewModel:
var myLiveData = ko.observableArray();
It took me a while to realize I couldn't just make myLiveData a normal array -- the ko.oberservableArray part was important.
Then you can go ahead and do whatever you want to myLiveData. For instance, make a $.getJSON call:
$.getJSON("http://foo.bar/data.json?callback=?", function(data) {
myLiveData.removeAll();
/* parse the JSON data however you want, get it into myLiveData, as below */
myLiveData.push(data[0].foo);
myLiveData.push(data[4].bar);
});
Once you've done this, you can go ahead and apply bindings using your ViewModel as usual:
function MyViewModel() {
var self = this;
self.myData = myLiveData;
};
ko.applyBindings(new MyViewModel());
Then in the HTML just use myData as you normally would.
This way, you can just muck with myLiveData from whichever function. For instance, if you want to update every few seconds, just wrap that $.getJSON line in a function and call setInterval on it. You'll never need to remove the binding as long as you remember to keep the myLiveData.removeAll(); line in.
Unless your data is really huge, user's won't even be able to notice the time in between resetting the array and then adding the most-current data back in.

I had a memory leak problem recently and ko.cleanNode(element); wouldn't do it for me -ko.removeNode(element); did. Javascript + Knockout.js memory leak - How to make sure object is being destroyed?

Have you thought about this:
try {
ko.applyBindings(PersonListViewModel);
}
catch (err) {
console.log(err.message);
}
I came up with this because in Knockout, i found this code
var alreadyBound = ko.utils.domData.get(node, boundElementDomDataKey);
if (!sourceBindings) {
if (alreadyBound) {
throw Error("You cannot apply bindings multiple times to the same element.");
}
ko.utils.domData.set(node, boundElementDomDataKey, true);
}
So to me its not really an issue that its already bound, its that the error was not caught and dealt with...

I have found that if the view model contains many div bindings the best way to clear the ko.applyBindings(new someModelView); is to use: ko.cleanNode($("body")[0]); This allows you to call a new ko.applyBindings(new someModelView2); dynamically without the worry of the previous view model still being binded.

<div id="books">
<ul data-bind="foreach: booksImReading">
<li data-bind="text: name"></li>
</ul>
</div>
var bookModel = {
booksImReading: [
{ name: "Effective Akka" },
{ name: "Node.js the Right Way" }]
};
ko.applyBindings(bookModel, el);
var bookModel2 = {
booksImReading: [
{ name: "SQL Performance Explained" },
{ name: "Code Connected" }]
};
ko.cleanNode(books);
ko.applyBindings(bookModel2, books);