Class: SC.Freezable

The SC.Freezable mixin implements some basic methods for marking an object as frozen. Once an object is frozen it should be read only. No changes may be made the internal state of the object.


To fully support freezing in your subclass, you must include this mixin and override any method that might alter any property on the object to instead raise an exception. You can check the state of an object by checking the isFrozen property.

Although future versions of JavaScript may support language-level freezing object objects, that is not the case today. Even if an object is freezable, it is still technically possible to modify the object, even though it could break other parts of your application that do not expect a frozen object to change. It is, therefore, very important that you always respect the isFrozen property on all freezable objects.


The example below shows a simple object that implement the SC.Freezable protocol.

Contact = SC.Object.extend(SC.Freezable, {

    firstName: null,

    lastName: null,

    // swaps the names
    swapNames: function() {
      if (this.get('isFrozen')) throw new Error(SC.FROZEN_ERROR);
      var tmp = this.get('firstName');
      this.set('firstName', this.get('lastName'));
      this.set('lastName', tmp);
      return this;


  c = Context.create({ firstName: "John", lastName: "Doe" });
  c.swapNames();  => returns c
  c.swapNames();  => EXCEPTION


Usually the SC.Freezable protocol is implemented in cooperation with the SC.Copyable protocol, which defines a frozenCopy() method that will return a frozen object, if the object implements this method as well.

Defined in: freezable.js

Field Summary

Instance Methods

Field Detail

isFreezable Boolean
Walk like a duck.
isFrozen Boolean

Set to YES when the object is frozen. Use this property to detect whether your object is frozen or not.

Instance Method Detail


Freezes the object. Once this method has been called the object should no longer allow any properties to be edited.

Documentation generated by JsDoc Toolkit 2.4.0 on Wed Apr 08 2015 10:02:20 GMT-0600 (CST)