I wanted to get attributes from model. I tried
this.model.get("group_description") and
this.model.models.get("group_description")
But none of them seem to work any help ? Below is snapshot of model structure...
your object d (this) is a Backbone.Collection, so you want
this.at(0).get("group_description")
Related
I'm creating a BreezeJS model and I would like to have an array as one of the property values, but I'm unsure how that would be set under the dataProperties section of the model. Would anyone have a example of how to do this?
Yo just define the property in your model as:
arrayOrObjectProperty: { dataType: "Undefined" }
And it should be enough, also if you require some further processing, like expansion or formatting of the property (so in your controllers the data is ready) you could do it in the jsonResultsAdapter.
I'm trying to retrieve the model, because I need to access certain attributes, but I cannot. I'm inside a view, which extends another one. This is how the view looks like:
var ImageGridControlView = GridControlView.extend({
//.... stuff ....
alert(this.model.get('property')) //This gives me an error in console and nothing is alerted.
});
In the class that the above code extends, the model can be retrieved, like this:
var GridControlView = ControlView.extend({
//.... stuff ....
alert(this.model.get('property')) //This shows the property value correctly
});
Why can't the model be retrieved from ImageGridControlView? What is the persistence of models across different classes, children, etc? I'm new to Backbone, and the official documentation only covers models superficially.
Your snippets are too small to actually find the problem, so we have to just guess. Most likely candidates are:
you are accessing this.model inside a function triggered by an event binding that is not properly bound, so this isn't actually your view instance. It could be a the source DOM element of the window object instead.
You aren't passing a model property in the options object provided to the view's constructor
What is the difference between properties and attributes of a Backbone model.
I believe one would use attributes to trigger model changes when the model gets modified.
In the below example.
var Vehicle = Backbone.Model.extend({prop1:'1'});
var v1 = new Vehicle({prop1 : '1111'});
console.log(v1.prop1); // accessing the property
console.log(v1.get('prop1')); // accessing the attribute
The object v1 has both a property called prop1 and also an attribute called prop1. There is no relation between them.
The difference is really that a property is a language feature (Javascript), whereas an attribute is a feature of the Backbone framework. To put it another way, a property exists independently of Backbone, whereas an attribute relies on the Backbone framework and its infrastructure.
Specifically, attributes participate in all the model-related things:
sync (when you call save or fetch)
validation on save
view rendering (via toJSON)
events and notification
I have 2 post collections and a model as follows.
# router file
#posts = new MyApp.Collections.PostsCollection()
#posts.reset options.posts
#followed_posts = new MyApp.Collections.PostsCollection()
#followed_posts.reset options.followed_posts
# Post model file
class MyApp.Models.Post extends Backbone.Model
paramRoot: 'post'
follow_post: ->
# ajax call
console.log "_________Index:#{this.collection.indexOf(this);}"
console.log this.collection
console.log "_________Followed:"
console.log #followed_posts
class MyApp.Collections.PostsCollection extends Backbone.Collection
model: MyApp.Models.Post
url: '/posts_all'
What I am trying to do is when one of the model changed in one collection, I want to update the other model in other collection too.
These collections may or may not hold same models.
So let's say if a model in #posts changed in my Post model, I want to update that model in #followed_posts too. If #followed_posts doesn't have that model, I need to add a duplicate of the model to #followed_posts collection.
I can access the collection that model belongs, but I cannot access the other collection.
Any ideas appreciated, thanks.
If the two collections are antisocial and can't talk directly to each other, which is usually good design, then you'll need an intermediary -- a global event dispatcher. When a model changes, propagate that event to the dispatcher along with a reference to the model. Listen for the event in the other collection and use the model passed to check for existence and respond as needed.
EDIT:
Backbone's documentation mentions this pattern:
For example, to make a handy event dispatcher that can coordinate
events among different areas of your application: var dispatcher =
_.clone(Backbone.Events)
But in fact, this is such a common pattern that the Backbone object itself is extended with Events. So you can just do:
// In your Post model
#on "change", -> Backbone.trigger "post:change", this, #collection
// And then something like this in the collection class definition:
#listenTo Backbone, "post:change", (model, collection) =>
if post = #get model.cid
post.set model.toJSON()
else
#add model
Also, is followed posts a subset of posts? If so, why not put an attribute on the model designating it as followed? Then you could find all followed posts with a simple filter function.
I would strongly suggest that you should consider having a single collection and add some kind of attribute in the model to differentiate between what kind of posts they are.
Here's the Example
I was following this excellent tutorial by Thomas Davis : What is a model?
Somehow the 'change' binding is not firing. What am I doing wrong here?
Backbone is checking if the set value is the same as the previous value (look at https://github.com/documentcloud/backbone/blob/master/backbone.js#L210 and on).
In your example, the array is still the same but the value inside changed. This is tricky to solve. Creating a new copy of the array seems to be overhead. I would suggest to call the change event directly in your adopt function as a solution:
adopt: function(newChildsName){
var children_array = this.get('children');
children_array.push(newChildsName);
this.set({children:children_array});
this.trigger("change:children");
}
I would suggest to create an issue on backbone github repository to maybe add a "force" option to force the update (thus triggering the event) of attributes on a model.
Here is a bit awkward solution:
adopt: function(newChildsName){
var children_array = this.get('children').splice(0);
children_array.push(newChildsName);
this.set({children:children_array});
}
Instead of using children as an plain array we can use it as an collection and listen to the add,remove events of the collection.