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
Related
This is my html
<input id="places-search" data-bind="textInput: str, event: {input: filter}" type="text" placeholder="Ex: Loft">
<div id="list-result">
<ul class="navbar-nav" data-bind="foreach: res">
<li class="nav-item">
<button class="nav-link btn btn-link" data-bind="attr: {title: elem}" onclick="popLWInfo(id)"></button>
And my javascript
<script>
var filterer = function(){
var self = this;
self.str = ko.observable("");
var location = function(data){
this.id = ko.observable(data.id);
this.marker = ko.observable(data.marker);
};
self.res = ko.observableArray();
for(var i = 0; i < markers.length; i++){
self.res.push(new location({id: i , marker: markers[i]}));
}
}
</script>
I tried using different words for the "foreach: res"
and i tried adding 'data-bind="with: filterer"'
but the array won't display
i still don't know what i am doing wrong
Without an example, it's hard to identify exactly what the issue is. If you could paste the entire example or create a JSFiddle then that would be great.
Although it might have been omitted from your original post, I don't see any call to ko.applyBindings which would handle taking your view model and applying it to the HTML.
// Insert this code after your function definition
(function(){
var model = new filterer();
ko.applyBindings(model);
})();
I am creating an edit screen where I want people to delete items from a list. The list is displayed normally, until the "controller" object goes into edit mode. Then the user can delete items. Items should be flagged for deletion and displayed as such, then when the user saves the edit, they are deleted and the server notified.
I actually have this all working, but the only way I could do it was using literal conditions in the bindings, which looks ugly and I don't really like. Is there a better way of doing it?
Working Fiddle: http://jsfiddle.net/L1e7zwyv/
Markup:
<div id="test">
<a data-bind="visible: IsViewMode, click: edit">Edit</a>
<a data-bind="visible: IsEditMode, click: cancel">Cancel</a>
<hr/>
<ul data-bind="foreach: Items">
<li data-bind="css: CssClass">
<span data-bind="visible: $parent.IsViewMode() || $data._Deleting(), text: Value"></span>
<!-- ko if: $parent.IsEditMode() && !$data._Deleting() -->
<input type="text" data-bind="value: Value"/>
<a data-bind="click: $parent.deleteItem">Del</a>
<!-- /ko -->
</li>
</ul>
</div>
Code:
function ItemModel(val)
{
var _this = this;
this.Value = ko.observable(val);
this._Deleting = ko.observable();
this.CssClass = ko.computed(
function()
{
return _this._Deleting() ? 'deleting' : '';
}
);
}
function ManagerModel()
{
var _this = this;
this.Items = ko.observableArray([
new ItemModel('Hell'),
new ItemModel('Broke'),
new ItemModel('Luce')
]);
this.IsEditMode = ko.observable();
this.IsViewMode = ko.computed(function() { return !_this.IsEditMode(); });
this.edit = function(model, e)
{
this.IsEditMode(true);
};
this.cancel = function(model, e)
{
for(var i = 0; i < _this.Items().length; i++)
_this.Items()[i]._Deleting(false);
this.IsEditMode(false);
};
this.deleteItem = function(model, e)
{
model._Deleting(true);
};
}
ko.applyBindings(new ManagerModel(), document.getElementById('test'));
you could:
wrap another span around to separate the bindings but this would be less efficient.
use both a visible: and if: binding on the same element to achieve the same functionality,
write a function on the itemModel isVisible() accepting the parent as an argument making your binding visible: $data.isVisible($parent).
Afterthought: If this comes up in multiple places you could write a helper function to combine visibility bindings
// reprisent variables from models
var v1 = false;
var v2 = false;
var v3 = false;
// Helper functions defined in main script body - globally accessible
function VisibilityFromAny() {
var result = false;
for(var i = 0; i < arguments.length; i++ ) result |= arguments[i];
return Boolean(result);
}
function VisibilityFromAll() {
var result = true;
for(var i = 0; i < arguments.length; i++ ) result &= arguments[i];
return Boolean(result);
}
// represent bindings
alert(VisibilityFromAny(v1, v2, v3));
alert(VisibilityFromAll(v1, v2, v3));
The third option is the most popular technique with MVVM aficionados like yourself for combining variables in a single binding from what I've seen, it makes sense and keeps all the logic away from the view markup in the view models.
Personally I like the syntax you have at present, (even though I count myself amongst the MVVM aficionado gang as well) this clearly shows in the view markup that the visibility of that element is bound to 2 items rather then hiding these details in a function.
I try to think of view models as a model for my view, not just a place where logic resides. When possible I also try to move complex logic back the view model and use descriptive names for my variables so the code is more readable.
I would suggest adding this to your view model -
var isViewable = ko.computed(function () { return IsViewMode() || _Deleting(); });
var isEditable = ko.computed(function() { return IsEditMode() && !_Deleting(); });
And in your view -
<li data-bind="css: CssClass">
<span data-bind="visible: isViewable, text: Value"></span>
<!-- ko if: isEditable -->
<input type="text" data-bind="value: Value"/>
<a data-bind="click: $parent.deleteItem">Del</a>
<!-- /ko -->
</li>
This cleans the bindings up and allows you to more easily adjust the logic without having to do many sanity checks in your view and view model both. Also I personally name variables that return a boolean such as this as isWhatever to help be more descriptive.
The benefit is that as your view and view model grow larger you can keep the DOM clean of clutter and also your view model becomes testable.
Here is a 'code complete' version of your fiddle with this added -
http://jsfiddle.net/L1e7zwyv/3/
I work on a search page that allows filtering, searching and paginating through the list of results. Each time list of currently displayed items is changed, knockout takes a lot of time to render new values. My knockout knowledge is limited but I can see in the DevTools that things are being handled very inefficiently:
item template is parsed for each element (no template caching?)
each item is inserted into the DOM separately (no bulk operations?)
Do you have any suggestions for fixing these issues?
I tried to extract the relevant code:
$.get("/api/Search/GetSearchResults?page=" + bla)
.then(function (result) {
self.contentListViewModel.load(result.SearchHits);
//...
});
//----------------
var ContentListViewModel = function (options) {
self.searchHits = ko.observableArray([]);
//...
this.load = function (elements) {
for (var i = 0; i < elements.length; i++) {
elements[i] = new ContentElementViewModel(elements[i]);
//...
}
self.searchHits(elements);
}
}
//----------------
var ContentElementViewModel = function (dto, options) {
//just setting couple of observable variables and couple of methods
}
Relevant HTML:
<ul data-bind="foreach: { data: searchHits, afterRender: afterRenderSearchHits }, as: 'hit', masonry: { enable: true, hits: searchHits }, css: { 'listify': !pinterestEnabled() }">
<li data-bind="template: { name: $data.template() }"></li>
</ul>
The answer is to avoid using 'template' binding. It triggers multiple jQuery.parseHTML calls that are expensive.
Slow code:
<ul id='list1' data-bind="foreach: { data: people }">
<li data-bind="template: 'item'"></li>
</ul>
<script id='item'>
<h3 data-bind="text: name"></h3>
</script>
Fast code:
<ul id='list2' data-bind="foreach: { data: people }">
<li>
<h3 data-bind="text: name"></h3>
</li>
</ul>
JS Bin example.
JS Perf
This response does not answer how to keep DOM manipulation to minimum, I'll ask another, more specific question for that.
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
I am new to Knockout and I am building a Simple POC for using knockout to build SPA(Single Page Application).
What I want to do is to show "Business Units" when the app loads and on selection of a business unit show all "Front End Units" under that business unit and on selection of a front end unit, show all "Sales Segments" under that front end unit.
All this will happen in a single page using the same view and the viewmodel will bind the model based on selected business unit or front end unit.
The issue I am facing is that, I have 5 business units that get bound properly first on document ready, but on selection of business unit, the front end units get repeated 5 times each. In this case, I have 2 front end units and each is shown 5 times. Same issue on selection of front end unit.
You can see this issue mimicked in the following jsFiddle sample - jsFiddle Link
Let me know if you can't access the jsfiddle link. In this sample, I have used arrays, but in actual I will be getting the data through async call to the oData service.
This is the view HTML:
<div id="divbu">
<h4 data-bind="text: Heading"></h4>
<ul data-role="listview" data-inset="true" data-bind="foreach: Collection">
<li data-role="list-divider" data-bind="text: EntityName"></li>
<li>
<a href="#" data-bind="click: $root.fnNextLevel">
<table border="0">
<tr>
<td>
<label style="font-size: 12px;">Bus. Plan: </label>
</td>
<td>
<label style="font-size: 12px;" data-bind="text: BusinessPlan"></label>
</td>
<td>
<label style="font-size: 12px;">Forecast: </label>
</td>
<td>
<label style="font-size: 12px;" data-bind="text: Forecast"></label>
</td>
</tr>
<tr>
<td>
<label style="font-size: 12px;">Gross Sales: </label>
</td>
<td colspan="3">
<label style="font-size: 12px;" data-bind="text: GrossSales"></label>
</td>
</tr>
</table>
</a>
</li>
</ul>
</div>
This is the model and view model:
function CommonModel(model, viewType) {
var self = this;
if (viewType == 'BU') {
self.EntityName = model[0];
self.BusinessUnit = model[0];
self.BusinessPlan = model[1];
self.Forecast = model[2];
self.GrossSales = model[3];
} else if (viewType == 'FEU') {
self.EntityName = model[1];
self.BusinessUnit = model[0];
self.FrontEndUnit = model[1];
self.BusinessPlan = model[2];
self.Forecast = model[3];
self.GrossSales = model[4];
} else if (viewType == 'SS') {
self.EntityName = model[2];
self.BusinessPlan = model[3];
self.Forecast = model[4];
self.GrossSales = model[5];
}
}
function ShipmentReportsViewModel(results, viewType) {
var self = this;
self.Collection = ko.observableArray([]);
for (var i = 0; i < results.length; i++) {
self.Collection.push(new CommonModel(results[i], viewType));
}
if (viewType == 'BU') {
self.Heading = "Business Units";
self.fnNextLevel = function (businessUnit) {
FetchFrontEndUnits(businessUnit);
};
self.Home = function () {
FetchBusinessUnits();
};
} else if (viewType == 'FEU') {
self.Heading = results[0][0];
self.fnNextLevel = function (frontEndUnit) {
FetchSalesSegments(frontEndUnit);
};
self.Home = function () {
FetchBusinessUnits();
};
} else if (viewType == 'SS') {
self.fnNextLevel = function () {
alert('No activity zone');
};
self.Heading = results[0][0] + ' - ' + results[0][1];
self.Home = function () {
FetchBusinessUnits();
};
}
}
You can see the complete code in the jsFiddle link.
I have also tried this with multiple views and multiple view models, where I apply bindings by giving the element ID. In this case, one flow from business unit -> sales segment is fine, but when I click on home or back button and I do binding again to that element, I face the same issue. (home and back button features are not done in jsFiddle example).
Let me know if more details are required. I did look into lot of other links in stack overflow, but nothing addressing this particular problem.
Any help is deeply appreciated. Thanks in advance.
The problem here is that you call your ko.applybindings TWICE and there is a foreach binding that iterate within 5 items, therefore the data are duplicated five times.
you should not call a ko.applybindings more than once on the same model.
Your model is always the same even if it's parametrized.
I had the same problem here: Data coming from an ObservableArray are displayed twice in my table
the fact that you have you business logic inside your viewModel is something that could be discussed, and it makes it not easy to fix this.
Make 3 classes, put them in a common model without logic inside. Then once you have applyed the ko.applyBindings once, you just have to modify the array like this:
viewModel.myArray(newValues)
Here is the fiddle with the amended code: http://jsfiddle.net/MaurizioPiccini/5B9Fd/17/
it does not do exaclty what you need but if remove the multiple bindings by moving the Collection object scope outside of your model.
As you can see the problem IS that you are calling the ko.applybindings twice on the same model.
Finally, I got this working. Thanks to #MaurizioIndenmark.
Though I have removed multiple call for ko.applybindings, I was still calling the view model multiple times. This was causing the issue.
Now, I have cleaner view model and I have different function calls for different actions and modify all the data required to be modified within these functions(events). Now, everything is working as expected.
This is how the view model looks now -
function ShipmentReportsViewModel(results) {
var self = this;
self.Heading = ko.observable();
self.BusinessUnits = ko.observableArray();
self.FrontEndUnits = ko.observableArray();
self.SalesSegments = ko.observableArray();
self.Home = function () {
var bu = FetchBusinessUnits();
self.Heading("Business Units");
self.BusinessUnits(bu);
self.FrontEndUnits(null);
self.SalesSegments(null);
};
self.fnFeu = function (businessUnit) {
var feu = FetchFrontEndUnits(businessUnit);
self.Heading(feu[0].BusinessUnit);
self.FrontEndUnits(feu);
self.BusinessUnits(null);
self.SalesSegments(null);
};
self.fnSalesSeg = function (frontEndUnit) {
var ss = FetchSalesSegments(frontEndUnit);
self.Heading(ss[0].BusinessUnit + ' - ' + ss[0].FrontEndUnit);
self.SalesSegments(ss);
self.BusinessUnits(null);
self.FrontEndUnits(null);
};
self.Home();
}
To see the entire working solution, please refer this jsFiddle
Thanks for all the valuable suggestions in getting this work.