Develop Reference

Ember and Handlebars Iterate Over a Set Array

I'm working on learning Ember and am trying to do some small ideas with it. Currently, I am trying to receive text field input to filter a list and return the matching results. I have all of this working, you know, the 'hard' stuff. However, the part that isn't working is Handlebars reading the 'title' property of my array that I am returning. It's just blank.
Here is my template:
<script data-template-name="application" type="text/x-handlebars">
{{input type="text" value=searchString placeholder="Search..."}}
{{filterMovies}}
<ul>
{{#each searchResults}}
<li>{{title}}</li>
{{/each}}
</ul>
</script>
And now my controller:
App.ApplicationController = Ember.Controller.extend({
filterMovies: function() {
var self = this,
searchString = self.get('searchString'),
searchResults = [],
filterArrLength = null,
theFullMovieList,
theFilteredMovieList = [];
if (!searchString) {
return;
}
var url = 'http://www.json-generator.com/api/json/get/clVKyWQSnC';
Ember.$.getJSON(url).then(function(data) {
theFullMovieList = data;
theFullMovieList.filter(function(movie) {
if (movie.title.toLowerCase().startsWith(searchString)) {
theFilteredMovieList.push(movie);
}
});
console.log(theFilteredMovieList);
self.set('searchResults', theFilteredMovieList);
});
}.property('searchString')
});
I have tried printing using {{this}}, {{this.title}}, {{searchResults.title}}, and {{title}} with no luck. However, logging the array shows the correct values.
Any ideas? View On CodePen

Your each syntax is invalid. You have to use new syntax:
<ul>
{{#each searchResults as |movie|}}
<li>{{movie.title}}</li>
{{/each}}
</ul>
See working demo on CodePen.

Knockout multiple click bindings do not work with IE8

The problem:
Multiple click binding do not work in IE8.
The code:
var Cart = function() {
var self = this;
self.books = ko.observableArray();
self.cds = ko.observableArray();
};
var TheModel = function() {
var self = this;
self.cart = ko.observable(new Cart());
self.showAddBook = function() {
self.cart.books.push(/* new book */);
};
self.showAddCD = function() {
self.cart.cds.push(/* new cd */);
};
};
<div data-bind="with: cart">
<h1>Books<h1>
<button data-bind="click: $parent.showAddBook">Add</button>
<div data-bind="foreach: books">
<span data-bind="text: name"></span> <!-- book has a name property -->
</div>
<hr/>
<h3>CDs</h3>
<button data-bind="click: $parent.showAddCD">Add</button>
<div data-bind="foreach: cds">
<span data-bind="text: name"></span> <!-- cd has a name property -->
</div>
</div>
Background:
Apologies in advance. I don't have access to jsFiddle at work.
I have a deadline to get this piece of work complete which is why I am using knockout with jQuery. Would love to use Angular but can't because we have to support IE8. Would love to use Durandal but I have no experience of it and don't have the time just yet to learn it and finish this piece of work.
A user can create a new book or a new cd and add it to a collection. Not real-world example but reflects the problem I am solving.
A user can click on an Add button, this launches a jQuery dialog which captures some information about a book. This is then saved to the observable array on the model, and the list of books gets updated.
Question:
Why does IE8 only seem to bind the first click and not the second? If I click to add a book the dialog is shown. If I click to add a cd, nothing. I have debugged and the function does not get called.
TIA

As far as I can tell, neither of them should work, and not on any browser (rather than just not working on IE8), because both functions have the same problem: They don't unwrap cart:
self.cart.books.push(/* new book */);
// ^^^^^^
cart is an observable, so you need:
self.cart().books.push(/* new book */);
// ^^
...and similarly for the CDs stuff.
If you fix that, it works (even on IE8):
var Cart = function() {
var self = this;
self.books = ko.observableArray();
self.cds = ko.observableArray();
};
var TheModel = function() {
var self = this;
self.cart = ko.observable(new Cart());
self.showAddBook = function() {
self.cart().books.push({name: "New book " + (+new Date())});
};
self.showAddCD = function() {
self.cart().cds.push({name: "New CD " + (+new Date())});
};
};
ko.applyBindings(new TheModel(), document.body);
<div data-bind="with: cart">
<h1>Books<h1>
<button data-bind="click: $parent.showAddBook">Add</button>
<div data-bind="foreach: books">
<span data-bind="text: name"></span> <!-- book has a name property -->
</div>
<hr/>
<h3>CDs</h3>
<button data-bind="click: $parent.showAddCD">Add</button>
<div data-bind="foreach: cds">
<span data-bind="text: name"></span> <!-- cd has a name property -->
</div>
</div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.2.0/knockout-min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>

Apologies for slightly incorrect example but I had missed one level of nesting. My example is not a true reflection of my complex model and implementation but I worked out the cause of the problem.
My Cart in this example has a selectedItem property (an observable) of type object that has the array of books (observable array) and CDs (observable array).
var Items = function () {
this.books = ko.observableArray();
this.cds = ko.observableArray();
}
var Cart = function() {
this.selectedItem = ko.observable(new Items());
}
var Model = function () {
this.cart = new Cart();
}
I was using the knockout 'with' binding and setting the context to cart.selectedItem
<div data-bind="with: cart.selectedItem"> ... </div>
With this approach I noticed that only the first click (add book) was working. Clicking on Add CD was doing nothing.
I changed the context from cart.selectedItem to cart and set the foreach binding (that displays the list of books and cds) to selectedItem().books and selectedItem().cds and that worked in IE8 and other browser.
If I change the context using the knockout 'with' binding back to cart.selectedItem then only the first click works.
Hope that helps anyone else who encounters this problem.

binding knockout observable arrays to multiple <ul> elements

For a navigation menu, I have two groups of links, each group and link showing up or not dependent on a user's role. The roles are looked up when the link structure is being built and the list of links is built accordingly. The returned JSON gets parsed, put into observable arrays with no problem, but when I actually try and apply the bindings, the binding fails because the observables are blank. Here is the HTML...
<ul id="user-menu" class="menu" data-bind="foreach: areas">
<li>
<a data-bind="attr: { href: areaLink }">
<img data-bind="attr: { src: iconUri }" />
<span data-bind="text: areaName"></span>
</a>
</li>
</ul>
<ul id="admin-menu" class="menu" data-bind="foreach: adminAreas">
<li>
<a data-bind="attr: { href: areaLink }">
<img data-bind="attr: { src: iconUri }" />
<span data-bind="text: areaName"></span>
</a>
</li>
</ul>
Knockout view model in the background...
var navigation = (function() {
function Area() {
var self = this;
self.areaName = ko.observable();
self.areaLink = ko.observable();
self.iconUri = ko.observable();
self.sequenceNo = ko.observable();
self.isAdmin = ko.observable();
self.loadFromVM = function (vm) {
self.areaName(vm.name || '');
self.areaLink(vm.link || '');
self.iconUri(vm.iconUri || '');
self.sequenceNo(vm.sequenceNo || '');
self.isAdmin(vm.isAdmin);
}
}
function viewModel() {
var self = this;
self.areas = ko.observableArray([]);
self.adminAreas = ko.observableArray([]);
self.setup = function () {
var data = {}; // population with basic session data
$.getJSON('....php', { JSON.stringify(data) }, function (results) {
for (var i = 0; i < results.length; i++) {
var area = new Area();
area.loadFromVM(results[i]);
if (area.isAdmin()) {
self.adminAreas().push(area);
} else {
self.areas().push(area);
}
}
});
};
}
var vmInstance;
return {
setup: function () {
vmInstance = new viewModel();
vmInstance.setup();
ko.applyBindings(vmInstance, $('#user-menu')[0]);
ko.applyBindings(vmInstance, $('#admin-menu')[0]);
}
};
})();
And then I bring it together with this in the navigation view file...
navigation.setup();
So after I get my JSON back, parse it, and organize it when I loop through the success function of the $.getJSON method, putting a watch on self.areas() and self.adminAreas() does show that the arrays have the exact information I want them to. But by the time they have to be applied, calling vmInstance.areas().length or vmInstance.adminAreas().length returns zero. Even more oddly, putting in an alert with the length of the arrays right after the $.getJSON call but within the setup() function will cause the alert to fire first, show zeroes, then goes through the get, populates the array, then fires zeroes again.
Not exactly sure what's going on here, but I can't remember seeing this kind of behavior in another project so I'm not quite sure what I'm doing wrong here. Any ideas or advice would be greatly appreciated.
EDIT: Nevermind on the Fiddle. It doesn't really capture my actual error.

adminarea object is not initialized.you made the adminArea variable but instead of this you have used same area variable to set values.
var adminArea = new Area();
adminArea.areaName('test admin area');
adminArea.areaLink('#');
adminArea.iconUri('http://evernote.com/media/img/getting_started/skitch/windows8/win8-checkmark_icon.png');
adminArea.sequenceNo(1);
adminArea.isAdmin(true);
Fiddle Demo

Create checkbox list from array of objects with knockout

I would like to know what is the proper way to create a list of checkboxes bound to a selected list for an array of objects using knockout. It is very straight forward using basic values like a list of words but can it be done with an array of objects.
this works:
<script type="text/JavaScript">
function ViewModel(){
self.choices = ["one","two","three","four","five"];
self.selectedChoices = ko.observableArray(["two", "four"]);
self.selectedChoicesDelimited = ko.dependentObservable(function () {
return self.selectedChoices().join(",");
});
}
</script>
<ul class="options" data-bind="foreach: choices">
<li><input type="checkbox" data-bind="attr: { value: $data }, checked: selectedChoices" /><span data-bind="text: $data"></span></li>
</ul>
<div data-bind="text: selectedChoicesDelimited"></div>
But I can't figure out how to get it to work if the items are objects like this:
self.choices = [{"Id":1,"Name":"one"},{"Id":2,"Name":"two"}, {"Id":3,"Name":"three"}, {"Id":4,"Name":"four"}, {"Id":5,"Name":"five"}];
self.selectedChoices = ko.observableArray([{"Id":2,"Name":"two"}, {"Id":4,"Name":"four"}]);
In the end I would like to be able to create checkbox lists from MultiSelectList object created in my MVC controller and passed to the view in the ViewBag.
#ebohlman answer about using CheckedValue is what I was looking for. One other note however, is that specifying the SelectedChoices directly as I did above will not work because the objects will not equal the objects in the Choices array even though the values in them are the same. Instead I've added code to push the selected choices onto the SelectedChoices array after defining it:
self.choices = [{"Id":1,"Name":"one","Selected":true},{"Id":2,"Name":"two","Selected":false}];
self.selectedChoices = ko.observableArray();
$.each(self.choices, function (index, value) {
if(value.Selected) self.selectedChoices.push(value);
});

Use the checkedValue binding:
<li>
<input type="checkbox" data-bind="checkedValue: $data, checked: $root.selectedChoices" />
<span data-bind="text: Name"></span>
</li>
And pick out the Name values when calculating the delimited string:
self.selectedChoicesDelimited = ko.computed(function () {
return ko.utils.arrayMap(self.selectedChoices(), function(v) {
return v.Name;
}).join(",");
});

Knockout foreach binding not working

I'm following John Papa's jumpstart course about SPA's and trying to display a list of customers loaded via ASP.NET Web API the knockout foreach binding is not working. The Web API is working fine, I've tested it on it's own and it is returning the correct JSON, because of that I won't post the code for it. The get method simply returns one array of objects, each with properties Name and Email. Although not a good practice, knockout is exposed globaly as ko by loading it before durandal.
I've coded the customers.js view model as follows
define(['services/dataservice'], function(ds) {
var initialized = false;
var customers = ko.observableArray();
var refresh = function() {
return dataservice.getCustomers(customers);
};
var activate = function() {
if (initialized) return;
initialized = true;
return refresh();
};
var customersVM = {
customers: customers,
activate: activate,
refresh: refresh
};
return customersVM;
});
The dataservice module I've coded as follows (I've not wrote bellow the function queryFailed because I know it's not being used)
define(['../model'], function (model) {
var getCustomers = function (customersObservable) {
customersObservable([]);
var options = {url: '/api/customers', type: 'GET', dataType: 'json'};
return $.ajax(options).then(querySucceeded).fail(queryFailed);
function querySucceeded(data) {
var customers = [];
data.forEach(function (item) {
var c = new model.Customer(item);
customers.push(c);
});
customersObservable(customers);
}
};
return {
getCustomers: getCustomers
};
});
Finaly the model module was built as follows:
define(function () {
var Customer = function (dto) {
return mapToObservable(dto);
};
var model = {
Customer: Customer
};
return model;
function mapToObservable(dto) {
var mapped = {};
for (prop in dto)
{
if (dto.hasOwnProperty(prop))
{
mapped[prop] = ko.observable(dto[prop]);
}
}
return mapped;
}
});
The view is then simply a list, it is simply:
<ul data-bind="foreach: customers">
<li data-bind="text: Name"></li>
</ul>
But this doesn't work. Any other binding works, and I've looked on the console window, and it seems the observable array is being filled correctly. The only problem is that this piece of code doesn't show anything on screen. I've reviewed many times the files but I can't seem to find the problem. What's wrong with this?

You can use the knockout.js context debugger chrome extension to help you debug your issue
https://chrome.google.com/webstore/detail/knockoutjs-context-debugg/oddcpmchholgcjgjdnfjmildmlielhof

Well, I just spent a lot of time on an local issue to realize that the ko HTML comment format, if used, should be like this:
<!-- ko foreach: arrecadacoes -->
and NOT like this:
<!-- ko: foreach: arrecadacoes -->
: is NOT used after ko...

I know this question is a little old but I thought I'd add my response in case someone else runs into the same issue I did.
I was using Knockout JS version 2.1.0 and it seems the only way I can get the data to display in a foreach loop was to use:
$data.property
so in the case of your example it would be
$data.Name
Hope this helps

I don't see anywhere in your code that you've called ko.applyBindings on your ViewModel.

KO has a known issue while using foreach in a non-container element like the one above <ul> so you have to use containerless control flow syntax.
e.g.
<ul>
<!-- ko foreach: customers-->
<li data-bind="text: Name"></li>
<!-- /ko -->
</ul>
Ref: http://knockoutjs.com/documentation/foreach-binding.html