    /**
     * Represents a filter that can be applied to a {@link Ext.util.MixedCollection MixedCollection}. Can either simply
     * filter on a property/value pair or pass in a filter function with custom logic. Filters are always used in the
     * context of MixedCollections, though {@link Ext.data.Store Store}s frequently create them when filtering and searching
     * on their records. Example usage:
     *
     *     //set up a fictional MixedCollection containing a few people to filter on
     *     var allNames = new Ext.util.MixedCollection();
     *     allNames.addAll([
     *         {id: 1, name: 'Ed',    age: 25},
     *         {id: 2, name: 'Jamie', age: 37},
     *         {id: 3, name: 'Abe',   age: 32},
     *         {id: 4, name: 'Aaron', age: 26},
     *         {id: 5, name: 'David', age: 32}
     *     ]);
     *
     *     var ageFilter = new Ext.util.Filter({
     *         property: 'age',
     *         value   : 32
     *     });
     *
     *     var longNameFilter = new Ext.util.Filter({
     *         filterFn: function(item) {
     *             return item.name.length > 4;
     *         }
     *     });
     *
     *     //a new MixedCollection with the 3 names longer than 4 characters
     *     var longNames = allNames.filter(longNameFilter);
     *
     *     //a new MixedCollection with the 2 people of age 32:
     *     var youngFolk = allNames.filter(ageFilter);
     *
     */
    Ext.define('Ext.util.Filter', {

        /* Begin Definitions */

        /* End Definitions */
        /**
         * @cfg {String} property
         * The property to filter on. Required unless a {@link #filterFn} is passed
         */

        /**
         * @cfg {Function} filterFn
         * A custom filter function which is passed each item in the {@link Ext.util.MixedCollection} in turn. Should return
         * true to accept each item or false to reject it
         */

        /**
         * @cfg {Boolean} anyMatch
         * True to allow any match - no regex start/end line anchors will be added.
         */
        anyMatch: false,

        /**
         * @cfg {Boolean} exactMatch
         * True to force exact match (^ and $ characters added to the regex). Ignored if anyMatch is true.
         */
        exactMatch: false,

        /**
         * @cfg {Boolean} caseSensitive
         * True to make the regex case sensitive (adds 'i' switch to regex).
         */
        caseSensitive: false,

        /**
         * @cfg {String} root
         * Optional root property. This is mostly useful when filtering a Store, in which case we set the root to 'data' to
         * make the filter pull the {@link #property} out of the data object of each item
         */

        /**
         * Creates new Filter.
         * @param {Object} [config] Config object
         */
        constructor: function(config) {
            var me = this;
            Ext.apply(me, config);

            //we're aliasing filter to filterFn mostly for API cleanliness reasons, despite the fact it dirties the code here.
            //Ext.util.Sorter takes a sorterFn property but allows .sort to be called - we do the same here
            me.filter = me.filter || me.filterFn;

            if (me.filter === undefined) {
                if (me.property === undefined || me.value === undefined) {
                    // Commented this out temporarily because it stops us using string ids in models. TODO: Remove this once
                    // Model has been updated to allow string ids

                    // Ext.Error.raise("A Filter requires either a property or a filterFn to be set");
                } else {
                    me.filter = me.createFilterFn();
                }

                me.filterFn = me.filter;
            }
        },

        /**
         * @private
         * Creates a filter function for the configured property/value/anyMatch/caseSensitive options for this Filter
         */
        createFilterFn: function() {
            var me       = this,
                matcher  = me.createValueMatcher(),
                property = me.property;

            return function(item) {
                var value = me.getRoot.call(me, item)[property];
                return matcher === null ? value === null : matcher.test(value);
            };
        },

        /**
         * @private
         * Returns the root property of the given item, based on the configured {@link #root} property
         * @param {Object} item The item
         * @return {Object} The root property of the object
         */
        getRoot: function(item) {
            var root = this.root;
            return root === undefined ? item : item[root];
        },

        /**
         * @private
         * Returns a regular expression based on the given value and matching options
         */
        createValueMatcher : function() {
            var me            = this,
                value         = me.value,
                anyMatch      = me.anyMatch,
                exactMatch    = me.exactMatch,
                caseSensitive = me.caseSensitive,
                escapeRe      = Ext.String.escapeRegex;

            if (value === null) {
                return value;
            }

            if (!value.exec) { // not a regex
                value = String(value);

                if (anyMatch === true) {
                    value = escapeRe(value);
                } else {
                    value = '^' + escapeRe(value);
                    if (exactMatch === true) {
                        value += '$';
                    }
                }
                value = new RegExp(value, caseSensitive ? '' : 'i');
             }

             return value;
        }
    });