Why is the el undefined on a page refresh or page load? Is it because the el does not exict?
class ListView extends Backbone.View
className: 'channels-list'
el: '#main'
initialize: ->
console.log #el
# undefined
The element needs to be a tag name or element that already exists in the DOM. When a new view is created the _ensureElement function is called:
// Ensure that the View has a DOM element to render into.
// If `this.el` is a string, pass it through `$()`, take the first
// matching element, and re-assign it to `el`. Otherwise, create
// an element from the `id`, `className` and `tagName` properties.
_ensureElement: function() {
//...
}
To avoid this place the script tag below the element tag or wait for the document load event, for example using jQuery:
jQuery ->
class ListView extends Backbone.View
className: 'channels-list'
el: '#main'
initialize: ->
console.log #el
Or, as Vitaliy suggested, rest .el in the initialize function.
Exactly. If you define el it should be available in DOM structure
Inside initialize method you can set element again if it already exists in DOM:
#setElement $('#main')
Related
I have some code which defines a backbone view being loaded as soon as a web page is loaded. The JavaScript is possibly executed before the DOM is fully loaded. If the dom element which becomes $el is not available when the code that defines the view is run is this a problem?
Programmatically I have something like this:
var view = Backbone.View.extend({
el: jQuery("#test")
events: {
}
render: function() {
this.$el.html();
}
//other view code
});
return view;
//some time passes
//with the view rendered above I now call :
view.render()
the problem is that when the render method is called this.$el is undefined. This is because when the first block of code was executed #test had not been loaded into the DOM. So; when the function Backbone.View.extend is called the 'el' element has to be loaded?
The context of this is a backbone application loaded via AMD. The first block of code is in a module. The module is 'required' before the DOM is loaded. Is this a common problem? How is it normally dealt with?
Thanks
el should not be a jQuery object but only a selector, $el will be the jQuery object for that selector. Also the id you specify as the el has to be found at initialization. So yes, the element has to be in the dom before you make it the el for the view.
If you're not creating / populating the view before making it a Backbone view you could do something like this to have backbone create the html tags etc. for you:
var view = Backbone.View.extend({
tagName: 'div',
id: 'test',
events: {
},
render: function() {
this.$el.html();
},
//other view code
});
You could then use templates to populate the view in your render function.
Short answer: Yes, the view element has to be loaded into the DOM when you initialize the view.
I am confused about why '''el''' is undefined here, and $el is defined.
The background is en experiment with CoffeeScript as follows:
class FastTodo.Views.AddTodoItem extends Backbone.View
template: JST['todo_items/add_item']
el: $('#main')
render: ->
console.log("render")
console.log($("#main"))
console.log(#el)
console.log(#)
$(#el).html #template
initialize: ->
#render()
How can I render the view in this case?
Try rewriting the element declaration to el: '#main'
I think that should work well for you.
By the way, according to your console log the jQuery element ($el) is empty as well. You must be declaring the view before the markup has been fully loaded. By giving el the selector for the elements you make sure it will be fetched only when the document is ready (loaded).
It is pretty basic thing but I still can't find the answer. I need to set View's el: to div which is in underscore.js template.
<script id="product" type="text/template">
<div class="productInfo"></div>
<div class="prices"></div>
<div class="photos"></div>
</script>
The first view renders the product template. I need to render other Views to divs in this template. I don't know how to set el:, because el: '.prices' just don't work with divs in template.
This Views structure is similar to How to handle initializing and rendering subviews in Backbone.js?. But I use template instead of rendering to existing divs.
So the problem is using a CSS selector string for this.el won't find anything if the matching <div> is not attached to the page's DOM. In the case of you <script> tag template, the contents of the <script> tag are not attached DOM nodes, there are just a single text node.
One option given your HTML would be to just forget about the <script> tag and put your empty <div> tags straight into the HTML. They are empty and thus should be harmless and invisible until you actual render some content within them. If you do that, el: '.productInfo:first' should work fine.
Other than that, you'll need to put logic into your parent view along these lines:
Render the template into a detached DOM node
Search that detached DOM node for subview divs
Map the subview div to the corresponding backbone view subclass
instantiate and render the subview, then use something like this.$el.find('.productInfo').replaceWith(productInfoView.el) to put the rendered HTML into the parent view at the right location
My general comment is that views should render to detached DOM nodes and leave it to other components such as the router or layout managers to decide where in the real DOM they get attached. I think this makes the views more reusable and testable.
Render the parent view, then assign the '.prices' as the el of the child:
var ParentView = Backbone.View.extend({
render : function() {
var html='<h1>Parent View</h1><div class="productInfo"></div><div class="prices"></div><div class="photos"></div>';
this.$el.html(html);
var prices = new PricesView({
el : this.$('.prices')
});
prices.render();
}
});
var PricesView = Backbone.View.extend({
render : function() {
var html='<h2>Prices View</h1>';
this.$el.html(html);
}
});
// Create a parent view instance and render it
var parent = new ParentView({
el : $('.parent')
});
parent.render();
Working example on jsfiddle: http://jsfiddle.net/JpeJs/
from version 0.9.9, backbone alaws you to define the el property of a view as a function :
When declaring a View, options, el and tagName may now be defined as functions, if you want their values to be determined at runtime.
Assuming that the subviews are created after the main view, this might help you if your subviews are aware of their parent :
SubView = Backbone.View.extend({
el : function(){
return this.parent.$('.prices');
}
});
var subViewInstance = new SubView({parent : theParentView});
I know Backbone.js's View object has parameters like id, tagName, className.
var DocumentRow = Backbone.View.extend({
tagName: "li",
className: "document-row",
});
It uses these for the insert template's parent element. When I do not set them, it will add a <div> to the template as the template's parent.
But it really annoys me because sometimes I don't need the parent! All I need I already have in my template, so how can I cancel it?
var DocumentRow = Backbone.View.extend({
el:'#your-element-id' //or class or type
});
This states that the view is to be bound to a pre-existing element as specified by the el property. Look up the docs at backbonejs.org
Since you already have it in your template just create and bind this view to it "after" the template is created (perhaps in a separate function?)
I have model Post and collection Posts. And want to make form with list of all post in <select id="multi" multiple="multiple">. So i have to make a PostView render inside my #multi with just this template:
<option value=""><%= title %></option>
But finally I get it wrapped with div. Is there any solution for not wrapping this template with <div>?
If you don't define an el (or tagName) for the view (in the class or during instantiation) the view will be placed inside a div tag. http://documentcloud.github.com/backbone/#View-el
var PostView = Backbone.View.extend({
tagName: 'option'
});
UPDATE
Starting v0.9.0, Backbone has view.setElement(element) to get this done.
var PostView = Backbone.View.extend({
initialize: function() {
var template = _.template('<option value=""><%= title %></option>');
var html = template({title: 'post'});
this.setElement(html);
}
});
If you don't want to have the view wrap your HTML, you'll have to do a few things:
Replace this.el entirely
Call delegateEvents on the new el
render: function(){
var html = "some foo";
this.el = html;
this.delegateEvents(this.events);
}
Since Backbone generates a div or other tag (based on your tagName setting for the view), you have to replace it entirely. That's easy to do. When you do that, though, you lose your declared events because Backbone uses jQuery's delegate under the hood to wire them up. To re-enable your declared events, call delegateEvents and pass in your events declarations.
The result is that your view.el will be the <option> tag that you want, and nothing more.
In version 0.9.0, Backbone introduced view.setElement(element) to handle this operation.