Revertible Observable

knockout-revertible.js

/* Small Knockout Extension to allow for canceling/confirming
 * changes to the view model. Defaults to the changed option.  Based on code sample from Ryan Niemeier
 *  http://www.knockmeout.net/2011/03/guard-your-model-accept-or-cancel-edits.html
 *
 * Please note: You should not use this unless you are 
 * explicitly confirming or resetting the values in every scenario before you
 * reference them again.  An unwanted revert may occur if you make changes without confirming and then cancel at a later point.
 */

 //wrapper to an observable that requires accept/cancel
    ko.revertibleObservable = function(initialValue) {
        //private variables
        var _actualValue = initialValue,
            _tempValue = ko.observable(initialValue);

        //computed observable that we will return
        var result = ko.computed({
            //always return the current value
            read: function() {
               return _tempValue();
            },
            //stored in a temporary spot until commit
            write: function(newValue) {
                 _tempValue(newValue);
            }
        });

        //if different, commit temp value
        result.commit = function() {
            if (_tempValue() !== _actualValue) {
                _tempValue.valueHasMutated();
                 _actualValue = _tempValue();
            }
        };

        //force subscribers to take original
        result.reset = function() {
            _tempValue(_actualValue);   //reset temp value
        };

        return result;
    };