I am creating a generic table view that can be used with different collections. Here is an example of what I'm trying to do:
...
getModelIdAttribute: function () {
return this.collection.__proto__.model.prototype.idAttribute;
},
getModelFromRow: function (HTMLrow) {
return this.collection.get(this.dataTable.row(HTMLrow).data()[this.getModelIdAttribute()]);
},
...
The data() function returns an object with the attributes that were used to create the model, but I want to account for different idAttributes.
Currently, my way works - but __proto__ is deprecated and it seems like there should be an easier way that I am missing?
Thanks
Here is what I am trying to understand.
Often times I find myself writing backbone like this:
var CallModel = Backbone.Model.extend({
});
var CallsCollection = Backbone.Collection.extend({
model: CallModel,
url: 'url/to/external/json'
});
It is a very basic example but as you can see, there is nothing really in the model all the data is coming into the Collection via an external url call to a json file that is build from a database.
So whats the purpose of the model? I am sure that I am probably not using backbone.js to its fullest extent which is why I am here asking you guys.
First of all, "there is nothing really in the model all the data is coming into the Collection via an external url call" - this is not true.
Let's assume you've the following:
//Model
var CallModel = Backbone.Model.extend({
defaults: {
cost:0,
duration:0
}
});
(without custom attributes or methods, there is no point in extending the original Backbone.Model)
//Collection
var CallsCollection = Backbone.Collection.extend({
model: CallModel,
url: 'url/to/external/json'
});
And the json data returned from service, probably something like:
//Response
{
callSummary: {
missed: 2,
received: 3,
totalCalls:5
totalDuration: 20
}
calls: [{
id:001,
caller:"Mr.A",
callee:"Mr.B",
cost:1,
duration:5
},{
id:002,
caller:"Mr.X",
callee:"Mrs.Y",
cost:1,
duration:7
},{
id:003,
caller:"Mr.A",
callee:"Mrs.B",
cost:1,
duration:8
}],
//and more additional information from your db
}
Now you populate your collection with data by calling it's fetch method:
CallsCollection.fetch();
Your collection should look something like:
{
models: [{
attributes: {
callSummary: {},
calls: [{},{},{}],
...
},
...
}],
length:1,
url: "url/to/external/json",
...
}
The data will be added to a model's attribute hash. If you don't specify a particular model, as Bart mentioned in his answer, backbone will populate the collection with a Backbone.Model instance: Which is still not much useful - Wew... A collection with single model having entire response data inside it's attributes as it is...
At this point, you're wondering why did I even bother creating a model, and then a collection..?
The problem here is Collections are derived from Arrays, while Models are derived from Objects. In this case, our root data structure is an Object (not an Array), so our collection tried to parse the returned data directly into a single model.
What we really want is for our collection to populate its models from the "calls" property of the service response. To address this, we simply add a parse method onto our collection:
var CallsCollection = Backbone.Collection.extend({
model: CallModel,
url: 'url/to/external/json',
parse: function(response){
/*save the rest of data to corresponding attributes here*/
return response.calls; // this will be used to populate models array
}
});
Now your collection will be something like the following:
{
models: [{
...
attributes: {
...
id:001,
caller:"Mr.A",
callee:"Mr.B",
cost:1,
duration:5
}
},{
...
attributes: {
...
id:002,
caller:"Mr.X",
callee:"Mrs.Y",
cost:1,
duration:7
}
},{
...
attributes: {
...
id:003,
caller:"Mr.A",
callee:"Mrs.B",
cost:1,
duration:8
}
}],
length:3,
url: "url/to/external/json",
...
}
This - is what we want! : Now it is very easy to handle the data: You can make use of the add, remove, find, reset and handful of other collection methods effectively.
You can pass this models array into your templating library of choice, probably with two way bindings: When the respective view for one of the call model changes, the particular model will be updated, events will propagate from your models to the collection, and the particular model will be passed into the handler functions.
You can now call fetch, save, destroy, clear and a lot of other methods with ease on single unit's of data (each model), rather than hurdle with the entire data saved in a single model - which is pretty much useless, you've to iterate through the response data manually and perform CRUD and similar operations by your own, and in most cases: re-render the entire collection view. which is very, very bad and totally unmaintainable.
To conclude: If your data source doesn't return an array of objects, or you don't parse the response and return an array of objects from which n number of models are to be populated - Then defining a collection is pretty much useless.
Hopefully, now you get the idea.
Very helpful source of info:
Backbone, The Primer: Models and Collections
Developing Backbone.js Applications
backbonejs.org
You don't need to specify a model. A Backbone collection will default to using Backbone.Model if you don't specify this option. The following would work equally well if you don't need the models of the collection to be of a particular instance.
var CallsCollection = Backbone.Collection.extend({
url: 'url/to/external/json'
});
Reference
EDIT
In essence, specifying the model option within a collection is just a way to ensure that objects added to this collection will be instances of that particular model class. If the models being added to your collection don't have any custom behaviour outside of what is available to Backbone.Model, you don't need to create and specify a model as Backbone collections will default to using an instance of Backbone.Model as I have already mentioned. If, however, you wanted to ensure that models added to a particular collection were of a particular type and shared customized behaviour (e.g. validations, defaults, etc.), you would create your own model class by extending Backbone.Model and specifying this in the collection. I hope this clears things up for you.
Sounds Weird but this is the way.
Every collection in backbone, must represent a model, so basically a collections is a list of models.
Even if your model has no data, you need to indicate it when you create a Collection.
This is how backbone works for collections.
So I'm using Backbone for my web application and I'm having trouble figuring out how to work with nested models. I have a model based on a java class whos JSON would look something like this:
"AdminSettings":
{
"defaults": {
"deletable":true,
"transferable":false;
"issueLimit":1
}
"displaySettings": {
"tabs":2,
"amounts:[10,20]
}
}
Currently, I have an endpoint set up and a backbone model for the AdminSettings object. I was wondering if there was a specific way to get all the backbone benefits for the objects inside AdminSettings. For example, currently I have to use:
adminSettings.get("defaultValues").shareable
But I want to use:
adminSettings.get("defaultValues").get("shareable")
This isn't the only benefit I'm trying to obtain, just an example.
So yeah, what would be a good way to go about this. I was thinking making a backbone model for each one of the nested objects and setting up endpoints for each one of those, but I'm not completely sure. Anyways, thanks for looking.
You could write your own custom backbone parser:
var DisplaySettingsModel = Backbone.Model.extend({});
var DefaultValuesModel = Backbone.Model.extend({});
var AdminSettingsModel = Backbone.Model.extend({
model: {
defaultValues: DefaultValuesModel
displaySettings: DisplaySettingsModel
},
parse: function(response){
response["defaultValues"] = new DefaultValuesModel(response["defaultValues"], {parse:true});
response["displaySettings"] = new DisplaySettingsModel(response["displaySettings"], {parse:true});
return response;
}
});
Is there a way to built more complex Model in Backbone.js, let me explain by an example :
This is a Json Session object :
{
id: "17",
notes: "",
start: "2012-10-18T15:57:41.511Z",
end: "2012-10-18T19:22:31.875Z",
sessionType: {
id: "1",
name: "Life Style",
}
}
When retrieving a Session Object from the server, I would like to have a SessionType Backbone.Model in order to add some business logic around this object.
So far I'm only able to retrieve an Object Session with a dummy SessionType, I can't add any logic on it because It doesn't belong to any Backbone model.
You can try this:
window.SessionType = Backbone.Model.extend({
initialize:function () {
},
});
Then in your session model, have a method:
window.Session = Backbone.Model.extend({
initialize:function () {
},
getSessionType () {
return new SessionType(this.get('sessionType'));
}
});
Now you can call the getSessionType() method which returns a model that can have your logic.
#Amulya is 100% correct. However, if you want the Session Model without having to call getSessionType(), I would look at using the the built in parse method and creating your model from there.
If your Session model is related to your model, I would look at using Backbone Relational. Since Backbone does not handle relationships, the plugin listed above does a fine job in filling the gap without too much manual labour.
I am working (for the first time) with Backbone.js in creating a reasonably simple application. I am currently working with two entities that have a one-to-many relationship:
Project: has many groups
Group: belongs to one project
I looked at a few different ways of representing relationships between models, from Backbone's own recommendations to Ligament to Backbone-relational. However, I eventually settled on using simple function calls. For example, within my 'Project' model, there's a function called groups():
groups: function() {
return new Collections.Groups(groups.where({project_id: this.get('id')}));
}
And within the Group model:
project: function() {
return projects.where({id: this.get('project_id')})[0];
}
This allows me to do things like:
var foo = new Project();
var foo_groups = foo.groups();
foo_groups.at(0).get('name');
var bar = new Group();
var bar_project = bar.project();
bar_project.get('name');
To me, the tradeoff here is the overhead of maintaining up-to-date relationships (when using something like backbone-relational) versus the processing time used calling the 'groups()' function each time you want to get a project's groups.
Can anyone advise me on any pitfalls I may encounter down the road as I build out more relationships in this way, perhaps recommending a better solution (other than the extensions mentioned above)? The application will eventually have about 6 entities with a variety of one-to-many and many-to-many relationships
Project.groups
I have an implementation of what I call AutoUpdatedCollection.
I use it in the scenario you have a shared Collection which contains every Model of one class, and this Collection is used to populate sub-Collections those have to be updated when the shared Collection is updated.
Check the implementation of the Backbone AutoUpdatedCollection.
Following your example I suppose there is a common/shared Collection called window.groups, then I'll implement Project Model like this:
// code simplified and no tested
var Project = Backbone.Model.extend({
initialize: function(){
this.groups =
new App.AutoUpdatedCollection({
name: "Project-" + this.id + "-groups",
sourceCollection: window.groups,
filterField: "project_id",
filterValue: this.id
}).filteredCollection;
this.groups.on( "add", this.addGroup, this );
this.groups.on( "remove", this.removeGroup, this );
}
});
Maybe is not as simple as this, if you have any problem let me know.
Group.project
I'd just initialize the Group.project attribute in the Group.initialize():
var Group = Backbone.Model.extend({
this.project = window.projects.where({id: this.get('project_id')})[0];
});