i am trying to make a two way binding in Knockout.js, but i am not pretty sure, that my approach is the right suggestion.
What i need is very simple:
I need the id of the binded element of my observable.
Here is my first approach:
HTML:
<div id='test' data-bind="attr {id: 'test'}, html: id"></div>
Javascript:
var vm = {
id: ko.observable()
};
ko.applyBindings(vm);
In the end, i need the id iformation in my viewmodel.
Maybe it´s not possible and not really reliable to knockout. But i dont want to go through the domtree with jquery selector if dont have the information in my viewmodel.
Thanks in advance
You need to give id in observable
id: ko.observable('test')
this will produce id
Fiddle Demo
From the comments on the original question, I don't think you're looking for two-way binding - you're looking for a way to cache the jQuery selector so that it can be accessed in your view model.
For that, I would suggest the following:
Add properties or variables in your view model that will hold the selector results. These do not need to be observables, as the IDs of your elements will never change.
Create a function that you call once on initialization of your view model, that will assign the results of the jQuery selectors to their respective properties/variables.
Subscribe to whatever observable contains the data, and trigger your animation from there.
Here's an example of how this could be done in your view model (JSFiddle example):
var ViewModel = ( function () {
var ViewModel = function () {
// ... stuff
this.data = ko.observable( 'No data here :(' );
this.data.subscribe( this.animate.bind( this ) );
};
// This is the function where you store the result of the jQuery selectors
ViewModel.prototype.cacheSelectors = function () {
this.testElement = $( '#test' );
};
// This is an example function that will load your data
ViewModel.prototype.loadData = function () {
this.data( 'Oh wait, here\'s some data!' );
};
// This is an example function that you could trigger to animate your element
ViewModel.prototype.animate = function () {
this.testElement.animate( { 'padding-left': '+=250px' }, 'slow' );
};
return new ViewModel();
}() );
ViewModel.cacheSelectors();
ko.applyBindings( ViewModel );
Related
I am bit new to knockout and jquery mobile, There was a question which is already answered, I need to optimize the PageStateManager class to use generic bindings, currently PageStateManager can only use for one binding,I would really appreciate if someone can guide me to create a generic class to manage page states with knockout bindings Heere is the working code,http://jsfiddle.net/Hpyca/14/
PageStateManager = (function () {
var viewModel = {
selectedHospital: ko.observable()
};
var changePage = function (url, viewModel) {
console.log(">>>>>>>>" + viewModel.id());
$.mobile.changePage(url, {viewModel: viewModel});
};
var initPage = function(page, newViewModel) {
viewModel.selectedHospital(newViewModel);
};
var onPageChange = function (e, info) {
initPage(info.toPage, info.options.viewModel);
};
$(document).bind("pagechange", onPageChange);
ko.applyBindings(viewModel, document.getElementById('detailsView'));
return {
changePage: changePage,
initPage: initPage
};
})();
Html
<div data-role="page" data-theme="a" id="dashBoardPage" data-viewModel="dashBoardViewModel">
<button type="button" data-bind="click: goToList">DashBoard!</button>
</div>
New dashboard model
var dashBoardViewModel = function() {
var self = this;
self.userName = ko.observable('Welcome! ' + "UserName");
self.appOnline = ko.observable(true);
self.goToList = function(){
//I would like to use PageStateManager here
// PageStateManager.changePage($("#firstPage"),viewModel);
ko.applyBindings(viewModel,document.getElementById("firstPage"));//If I click Dashbord button multiple times it throws and multiple bind exception
$.mobile.changePage($("#firstPage"));
}
}
ko.applyBindings(dashBoardViewModel,document.getElementById("dashBoardPage"));
update url : http://jsfiddle.net/Hpyca/14/
Thank you in advance
I would probably go for creating a NavigationService which only handles changing the page and let knockout and my view models handle the state of the pages.
An simple example of such a NavigationService could be:
function NavigationService(){
var self = this;
self.navigateTo = function(pageId){
$.mobile.changePage($('#' + pageId));
};
}
You could then, in your view models just call it when you want it to navigate to a new page. One example would be upon selection of a hospital (which could be done either via a selection function or by manually subscribing to changes to the selectedHospital observable):
self.selectHospital = function(hospital){
self.selectedHospital(hospital);
navigationService.navigateTo('detailsView');
};
Other than the call to the navigationService to navigate, it's just ordinary knockout to keep track of which viewmodel should be bound where. A lot easier than having jquery mobile keeping track of which viewmodel goes where, if you ask me.
I have updated your jsfiddle to show a sample of how this could be done, making as few changes as possible to the HTML code. You can find the updated fiddle at http://jsfiddle.net/Hpyca/15/
I have the following JavaScript code, which works as expected...
/** #jsx React.DOM */
var TreeView = React.createClass({
render: function() {
return <div ref="treeview"></div>;
},
componentDidMount: function() {
console.log(this.props.onChange);
var tree = $(this.refs.treeview.getDOMNode()).kendoTreeView({
dataSource: ...,
dataTextField: "Name",
select: this.props.onChange
}
});
}
});
var MyApp = React.createClass({
onChange: function(e) {
console.log(e);
this.setState({key: e});
},
render: function() {
return (
<div>
<TreeView onChange={this.onChange}/>
<GridView />
</div>
);
}
});
However, with the kendo treeview, on selecting a tree node, the whole node is passed. To get at the underlying key, I would need to process the node as follows:
select: function(e) {
var id = this.dataItem(e.node).id;
this.props.onChange(id);
}
However I've obviously not quite got it right since, and here please excuse my noobness, it seems that in the working instance a reference to the function is being used, whereas in the non-working instance, the function is actually being executed... Or something like that: the error message being returned is:
Cannot call method 'onChange' of undefined.
So what would I need to do to be able to reference the function which extracts the key before calling the onChange method? Note that, if my understanding is correct, onChange needs to be executed in the context of the MyApp class so that any child components will get notified on the change.
EDIT: I've tried using partial application but am still not quite there. I've updated the onChange routine to take a function which returns the key from the node
onChange: function(getKey, e) {
this.setState({Key: getKey(e)});
},
But am not sure how to wire it all up.
Your code looks mostly right. I believe your only problem is that the select callback you're passing to the treeview is being called with the wrong scope. Note that you're using this to mean two different things within the function (once for the actual tree view object and the other for the React component). Easiest solution is probably to store a reference to the onChange function like so:
componentDidMount: function() {
var onChange = this.props.onChange;
var tree = $(this.refs.treeview.getDOMNode()).kendoTreeView({
dataSource: ...,
dataTextField: "Name",
select: function(e) {
var id = this.dataItem(e.node).id;
onChange(id);
}
});
}
Hope this helps.
I need to pass data from a click: event into another div. Here is a scenario:
There is a link on one side of the page.
<a data-bind="text: Name, click: $root.editAction"></a>
On the other side of the page, there is a hidden div.
<div data-bind="if: $root.editActionShow">
<input type="text" data-bind="value: Name"/>
</div>
I need to be able to pass $data from the click: event, do that hidden div.
Perhaps I am over-thinking this, but my viewModel has many different Actions buried deep in viewModel.DataGroups.DataGroup.ActionDataGroup and there is only 1 HTML form to edit action information, so I can't figure out how to make the form only show that one particular action I want to edit.
Here is another kicker. I prefer not to add any observables to my viewModel. Reason being is that I have to do .toJS() map it at the end, and then convert JSON into XML, which must validate against a pretty strict schema, so having extra elements is a bad thing. It will not pass validation, unless I manually remove them before conversion. However, I can add this.blah = function() {} objects to my viewModel, because .toJS() strips them during conversion.
UPDATE:
Aaand solution to all this is hands down hilarious
viewModel.editAction = function(data) {
viewModel.editActionFormShow(true);
ko.applyBindings(data, $('#myHiddenDiv')[0]);
};
From what I understand, you want something like a 'click-to-edit' function, which can be solved pretty neatly with just 2 custom bindings!
The great advantage about this approach is you won't polute your viewModel with extra observables.
Bindings:
ko.bindingHandlers.hidden = {
update: function(element, valueAccessor) {
var value = ko.utils.unwrapObservable(valueAccessor());
ko.bindingHandlers.visible.update(element, function() {
return!value; });
}
};
ko.bindingHandlers.clickToEdit = {
init: function(element, valueAccessor,allBindingsAccessor){
var value = valueAccessor(),
input = document.createElement('input'),
link = document.createElement('a');
element.appendChild(input);
element.appendChild(link);
value.isEditing = ko.observable(false);
ko.applyBindingsToNode(link,{
text: value,
hidden: value.isEditing,
click: function(){
value.isEditing(true);
}
});
ko.applyBindingsToNode(input,{
value: value,
visible: value.isEditing,
hasfocus: value.isEditing
});
}
};
ViewModel
var vm = {
name: ko.observable()
}
The HTML
<div data-bind="clickToEdit: name"></div>
Working fiddle: http://jsfiddle.net/8Qamd/
All credit goes to Ryan Niemeyer.
How is it possible to make knockout data-bind work on dynamically generated elements? For example, I insert a simple html select menu inside a div and want to populate options using the knockout options binding. This is what my code looks like:
$('#menu').html('<select name="list" data-bind="options: listItems"></select>');
but this method doesn't work. Any ideas?
If you add this element on the fly after you have bound your viewmodel it will not be in the viewmodel and won't update. You can do one of two things.
Add the element to the DOM and re-bind it by calling ko.applyBindings(); again
OR add the list to the DOM from the beginning and leave the options collection in your viewmodel empty. Knockout won't render it until you add elements to options on the fly later.
Knockout 3.3
ko.bindingHandlers.htmlWithBinding = {
'init': function() {
return { 'controlsDescendantBindings': true };
},
'update': function (element, valueAccessor, allBindings, viewModel, bindingContext) {
element.innerHTML = valueAccessor();
ko.applyBindingsToDescendants(bindingContext, element);
}
};
Above code snippet allows you to inject html elements dynamically with the "htmlWithBinding" property. The child elements which are added are then also evaluated... i.e. their data-bind attributes.
rewrite html binding code or create a new. Because html binding prevents "injected bindings" in dynamical html:
ko.bindingHandlers['html'] = {
//'init': function() {
// return { 'controlsDescendantBindings': true }; // this line prevents parse "injected binding"
//},
'update': function (element, valueAccessor) {
// setHtml will unwrap the value if needed
ko.utils.setHtml(element, valueAccessor());
}
};
For v3.4.0 use the custom binding below:
ko.bindingHandlers['dynamicHtml'] = {
'update': function (element, valueAccessor, allBindings, viewModel, bindingContext) {
// setHtml will unwrap the value if needed
ko.utils.setHtml(element, valueAccessor());
ko.applyBindingsToDescendants(bindingContext, element);
}
};
EDIT: It seems that this doesn't work since version 2.3 IIRC as pointed by LosManos
You can add another observable to your view model using myViewModel[newObservable] = ko.observable('')
After that, call again to ko.applyBindings.
Here is a simple page where I add paragraphs dynamically and the new view model and the bindings work flawlessly.
// myViewModel starts only with one observable
var myViewModel = {
paragraph0: ko.observable('First')
};
var count = 0;
$(document).ready(function() {
ko.applyBindings(myViewModel);
$('#add').click(function() {
// Add a new paragraph and make the binding
addParagraph();
// Re-apply!
ko.applyBindings(myViewModel);
return false;
});
});
function addParagraph() {
count++;
var newObservableName = 'paragraph' + count;
$('<p data-bind="text: ' + newObservableName + '"></p>').appendTo('#placeholder');
// Here is where the magic happens
myViewModel[newObservableName] = ko.observable('');
myViewModel[newObservableName](Math.random());
// You can also test it in the console typing
// myViewModel.paragraphXXX('a random text')
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/2.2.1/knockout-min.js"></script>
<div id="placeholder">
<p data-bind="text: paragraph0"></p>
</div>
<a id="add" href="#">Add paragraph</a>
It's an old question but here's my hopefully up-to-date answer (knockout 3.3.0):
When using knockout templates or custom components to add elements to prebound observable collections, knockout will bind everything automatically. Your example looks like an observable collection of menu items would do the job out of the box.
Based on this existing answer, I've achived something similar to your initial intentions:
function extendBinding(ko, container, viewModel) {
ko.applyBindings(viewModel, container.children()[container.children().length - 1]);
}
function yourBindingFunction() {
var container = $("#menu");
var inner = $("<select name='list' data-bind='options: listItems'></select>");
container.empty().append(inner);
extendBinding(ko, container, {
listItems: ["item1", "item2", "item3"]
});
}
Here is a JSFiddle to play with.
Be warned, once the new element is part of the dom, you cannot re-bind it with a call to ko.applyBindings- that is why I use container.empty(). If you need to preserve the new element and make it change as the view model changes, pass an observable to the viewModel parameter of the extendBinding method.
Checkout this answer: How do define a custom knockout 'options binding' with predefined Text and Value options
ko.applyBindingsToNode is particularly useful.
I am stuck on the following issue:
I have a model with a property that defines if it is visibly selected or not, which I will call SelectModel for the purpose of this question.
SelectModel = Backbone.Model.extend({
defaults:{
isSelected: false
}
})
Now the first part that I do not really get is how I should handle the selection in general.
If I want to use the observer pattern, my View should listen to the change of the isSelected property. But my view also triggers this in the first place, so I would have.
SelectView = Backbone.View.extend({
initialize: function(){
this.model.bind("change:isSelected", this.toggleSelectionVisually)
},
events: {
"click" : toggleSelection
},
toggleSelection: function(){
this.model.set({"isSelected": !this.model.get("isSelected");
},
toggleSelectionVisually:(){
//some code that shows that the view is now selected
},
})
So this in itself already feels a bit absurd but I guess I just understand something wrong.
But the part which I really fail to implement without making my code horrible is handling the selection for multiple models that only one model is selected at a time.
SelectListView = Backbone.View.extend({
initialize: function(){
this.collection = new SelectList();
},
toggleSelection: function(){
????
}
})
So who should notify whom of the selection change? Which part should trigger it and which part should listen? I am really stuck on this one. For a single View it is doable, for a collection I am sadly lost.
I would have suggested the following simplification for your SelectView until I saw the second part of your question:
SelectView = Backbone.View.extend({
events: {
"click" : toggleSelection
},
toggleSelection: function(){
this.model.set({"isSelected": !this.model.get("isSelected");
//some code that shows whether the view is selected or not
}
});
However, since the isSelected attribute is apparently mutually exclusive, can be toggled off implicitly when another one is toggled on, I think the way you have it is best for your case.
So, using your existing SelectView and, you could have a SelectListView as follows. WARNING: it iterates over your entire collection of models each time one is selected. If you will have a large number of models this will not scale well, and you'll want to cache the previously-selected model rather than iterating over the entire collection.
SelectListView = Backbone.View.extend({
initialize: function(){
this.collection = new SelectList();
this.collection.bind('change:isSelected', this.toggleSelection, this);
},
toggleSelection: function(toggledModel){
//A model was toggled (on or off)
if(toggledModel.get('isSelected') {
//A model was toggled ON, so check if a different model is already selected
var otherSelectedModel = this.collection.find(function(model) {
return toggledModel !== model && model.get('isSelected');
});
if(otherSelectedModel != null) {
//Another model was selected, so toggle it to off
otherSelectedModel.set({'isSelected': false});
}
}
}
});
I would recommend that your model not keep track of this, but rather the view.
In my mind the model has nothing to do with its display, but rather the data that you're tracking. The view should encapsulate all the info about where and how the data is displayed to the user
So I would put isSelected as an attribute on the view. Then it's trivial to write a method to toggle visibility. If you then need to explain the other views that a specific view is selected you can attach a listener $(this.el).on('other_visible', toggle_show) which you can trigger on your toggle_visibility method with $(this.el).trigger('other_visible')
Very close to the solution suggested by #rrr but moving the logic from the View to the Collection where I think it bellows to:
SelectsCollection = Backbone.Collection.extend({
initialize: function() {
this.on( "change:selected", this.changeSelected );
},
changeSelected: function( model, val, opts ){
if( val ){
this.each( function( e ){
if( e != model && e.get( "selected" ) ) e.set( "selected", false );
});
};
},
});
There are different ways you could do it. You could trigger an event on the collection itself and have all the SelectModel instances listen for it and update themselves accordingly. That seems a bit wasteful if you have a lot of SelectModel instances in the collection because most of them won't end up doing any work. What I would probably do is keep track of the last SelectModel in your View:
SelectListView = Backbone.View.extend({
initialize: function(){
this.collection = new SelectList();
this.lastSelectedModel = null;
},
toggleSelection: function(){
// populate newSelectedModel with the SelectedModel that you're toggling
var newSelectedModel = getNewSelectedModel();
if (!newSelectedModel.get('isSelected')) {
// if the SelectModel isn't already selected, we're about to toggle it On
// so we need to notify the previously selected SelectModel
if (this.lastSelectedModel) {
this.lastSelectedModel.set({isSelected: false});
}
this.lastSelectedModel = newSelectedModel;
} else {
// if the newSelectedModel we're about to toggle WAS already selected that means
// nothing is selected now so clear out the lastSelectedModel
this.lastSelectedModel = null;
}
newSelectedModel.set({isSelected: !newSelectedModel.get('isSelected')});
}
})