ember.js - Ember Views and initializing with values - TypeError: this.currentState is undefined -

i having trouble working ember views , initializing them values before template rendered. code below, getting following error in browser:

typeerror: this.currentstate undefined this.currentstate.childviewsdidchange(this, views, start, added);

my question is, error message mean, , there approach work better?

app.smileyfaceview = ember.containerview.extend   childviews: null    init: () ->     @_super      happy = app.smileyface.create()     happy.setface(":)")      angry = app.angryface.create()     angry.setface(">:(")      blah = app.blahface.create()     blah.setface(":|")      @pushobject(happy)     @pushobject(angry)     @pushobject(blah)  app.smileyfaceview = ember.view.extend   tagname: "span"   template: null    setface: (face) ->     @set('template', ember.handlebars.compile(face))