How do I tell backbone that the model is not new

Question

I have an object that's also saved in the server and I'm creating a Backbone model from that object.

But when I save the model, it's doing a PUT request, which is not what I want. How to tell Backbone that the data is already in the server without doing a fetch?

Answer 1

Backbone determines the newness of a model by checking if an id is set :

isNew model.isNew()

Has this model been saved to the server yet? If the model does not yet have an id , it is considered to be new.

And when you save a model,

• if it is new, a POST request will be emitted,
• if it is an update (an id has been set), a PUT request will be sent

Backbone Sync documentation

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And as noted by @JayC in the comments :

If there's an issue that the id can't literally be id , you can use idAttribute to say which is the "identity" or key field.

Answer 2

Adding my two cents here, hope it avoids some hair pulling I had to do.

Setting a model's id property directly via constructor to false or null won't do the trick, you have to actually remove it from memory via via delete

For example, I just struggled to copy attributes from one model type to another type as a new model:

copy = Trip.clone()
#doesn't unset the id attribute
schedule = new models.Schedule(_.extend(copy.attributes, {id:null, trip_id:id})
#does unset the id attribute
delete schedule.id
schedule.save null, success: =>
  # back from POST vs PUT   
  ...