Question

Code:

  class Session extends Backbone.Model
    initialize: ->
      @bind 'change', @save
      console.log 'init'
  class SessionList extends Backbone.Collection
    model: Session
    localStorage: new Store 'sessions'

  sessions = new SessionList
  a = new Session x: 'test'
  sessions.add a    
  console.log a.get 'x'
  a.set x: 'new'
  console.log a.get 'x'

When loaded in a page with Backbone.localstorage, the console gives:

init
test
Uncaught TypeError: Cannot read property 'localStorage' of undefined
  backbone-localstorage.js:70
Backbone.sync
_.extend.save
  backbone-localstorage.js:70
Backbone.Events.trigger
  backbone.js:304
_.extend.change
  backbone.js:117

And when I comment out the @bind call, I get the expected:

init
test
new

I can also save manually successfully after a has been added to sessions with a call to a.save().

I guess the problem is that the Session constructor triggers the change event, and save() doesn’t know what to do before a has been added to sessions? So I could instead do something like this:

class Session extends Backbone.Model
  set: (fields, ops) ->
    super fields, ops
    if (this has been added to a Collection)
      @save() 

Is this the best way to do it? If yes, how do I fill in the if statement?

Answer 1

My suggestion would be to just call save instead of set. so replace this:

a.set x: 'new'

with

a.save x: 'new'

hope that works for you