CODEWITHSUNDEEP
javascriptbackbone.js
William Sham
William Sham

Reputation: 13239

Backbone.js collection

i'm a beginner to backbone.js

why would you want to use a COLLECTION?

Can't you just have a view associated with each model?

Also, does an event bond to a collection of model apply to all models?

Upvotes: 0

Views: 750

Answers (3)

lorefnon
lorefnon

Reputation: 13105

When you are operating on large datasets it is very much necessary to have a mechanism to perform operations on whole datasets or subsets. In Backbone.js Collection class provides this mechanism. A few very frequent usages of Collection may be outlined as follows :

  • Suppose you are fetching the results of a query from a database. Now you can create a model corresponding to the structure of record, define a collection, create a collection instance, define the url (and if required customize the ajax request) and then give a call to fetch. This is more advantageous to having an array of models : firstly it is more convenient than to iterate through the parsed json data structure and create a model from each record object. Secondly the entire collection can be updated at once to the server. As pointed out by Mario, it makes working with related records very convenient.

  • Secondly, Collection class provides you a base class which you can easily auxiliate with your functions to provide custom filtering and sorting capabilities.

  • You can have Views eg. data grids, trees etc to represent the collection. It is convenient to code and also think in terms of a view representing a collection.

Upvotes: 2

M. Lanza
M. Lanza

Reputation: 6790

You could use a collection is to represent a one-to-many relationship. This is type of thing is perfect when your backend datastore is a document database (having embedded documents).

You can also use a collection to allow for iteration over your models.

Since a model can only belong to a single collection it almost makes sense at times to treat a collection like a table in the database. In the database I have a people table. In my javascript I have a people collection.

(The reason a model can only belong to a single collection is that upon adding a model to a collection the collection stores a reference to itself directly on the model. Adding a model to a second collection would overwrite the model's reference to the first collection.)

Upvotes: 1

keyle
keyle

Reputation: 2837

You use them when you have nested models, see http://documentcloud.github.com/backbone/#FAQ-nested

I guess you could have a view associated with each model but not necessarily. Not sure about the last part, maybe run a quick test.

Upvotes: 1

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