how to unset an _id backbone model attribute?

Question

I would like to unset() the _id attribute from an instance of a model, to make a POST request using the save() model method.

But i get a Uncaught TypeError: Object [object Object] has no method 'call' backbone-min.js because of this line:

myModel.unset('_id');

I am using idAttribute: "_id" so i tried:

myModel.unset('id');

But it doesn't unset the _id attribute.

Answer 1

Using model.unset('_id') should work fine. My guess is that the error is thrown by a change event listener, either in your code or some library code. In order to not trigger events you can use the silent:true option.

However, if you simply want to force the model.save() method to perform a POST, you don't need to unset the _id attribute.

Instead override the model.isNew method. Backbone uses this to determine whether a model is new (and should be POSTed) or existing (and should be PUT). Overriding the method to always return true will make your model to be POSTed every time:

isNew: function() { return true; }

Answer 2

Backbone stores the attributes in an object called attributes within the model. The attribute _id, although representative of the ID of that model is not what is used to determine whether a model is new.

There is a property called id (sibling of attributes) which is what is used to make the isNew() determination.

If you want to force a POST, you'll need to delete the id property:

var id = model.id;
model.unset('_id');
delete model.id;
model.save(); // this will do a POST