骨干集合通过其ID获取模型

Question

I've problems getting a single Model by its ID even though I set the idAttribute in the coresponding Model.

A Collection looks like this:

[
    {
        "_account": "51dc04dbe4e643043d000001",
        "name": "test.png",
        "type": "image/png",
        "_id": "51ff833f0342ee0000000001",
        "added": "2013-08-05T10:49:35.737Z"
    }
]

// Inside the Model I defined idAttribute
FileModel = Backbone.Model.extend({

idAttribute : "_id",
urlRoot : "/api/file"

[...]

}
// The collection contain each of the Model items
// but if I try to get a single model item  by id:

Collection.get("51ff833f0342ee0000000001") -> the result is undefined

I cant figure out why and the solution from Backbone.Collection get model by id was not the key to solve the problem.

Answer 1

In order to retrieve a model by a custom id you need to specify on the model it's idAttribute and you need to specify the collection's model property to use your model. Normally it's enough to set this in your collection where you declare it's properties

var MyCollection = Backbone.Collection.extend({
  model: FileModel,
  ...
})

However depending on how you have your JavaScript laid out (and therefore how the JavaScript is evaluated by the browser) it is possible at the time the model: FileModel statement is read it is still undefined. To get around this you can move the assignment of the property to the initialize/constructor of your collection.

For example

var MyCollection = Backbone.Collection.extend({

        initialize: function () {
            this.model = FileModel;
        }
    ...
});