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.

Enforcement

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.

Example

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.freeze();
  c.swapNames();  => EXCEPTION

Copying

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

• freeze()