    /**
     * @author Ed Spencer
     *
     * Fields are used to define what a Model is. They aren't instantiated directly - instead, when we create a class that
     * extends {@link Ext.data.Model}, it will automatically create a Field instance for each field configured in a {@link
     * Ext.data.Model Model}. For example, we might set up a model like this:
     *
     *     Ext.define('User', {
     *         extend: 'Ext.data.Model',
     *         fields: [
     *             'name', 'email',
     *             {name: 'age', type: 'int'},
     *             {name: 'gender', type: 'string', defaultValue: 'Unknown'}
     *         ]
     *     });
     *
     * Four fields will have been created for the User Model - name, email, age and gender. Note that we specified a couple
     * of different formats here; if we only pass in the string name of the field (as with name and email), the field is set
     * up with the 'auto' type. It's as if we'd done this instead:
     *
     *     Ext.define('User', {
     *         extend: 'Ext.data.Model',
     *         fields: [
     *             {name: 'name', type: 'auto'},
     *             {name: 'email', type: 'auto'},
     *             {name: 'age', type: 'int'},
     *             {name: 'gender', type: 'string', defaultValue: 'Unknown'}
     *         ]
     *     });
     *
     * # Types and conversion
     *
     * The {@link #type} is important - it's used to automatically convert data passed to the field into the correct format.
     * In our example above, the name and email fields used the 'auto' type and will just accept anything that is passed
     * into them. The 'age' field had an 'int' type however, so if we passed 25.4 this would be rounded to 25.
     *
     * Sometimes a simple type isn't enough, or we want to perform some processing when we load a Field's data. We can do
     * this using a {@link #convert} function. Here, we're going to create a new field based on another:
     *
     *     Ext.define('User', {
     *         extend: 'Ext.data.Model',
     *         fields: [
     *             {
     *                 name: 'firstName',
     *                 convert: function(value, record) {
     *                     var fullName  = record.get('name'),
     *                         splits    = fullName.split(" "),
     *                         firstName = splits[0];
     *
     *                     return firstName;
     *                 }
     *             },
     *             'name', 'email',
     *             {name: 'age', type: 'int'},
     *             {name: 'gender', type: 'string', defaultValue: 'Unknown'}
     *         ]
     *     });
     *
     * Now when we create a new User, the firstName is populated automatically based on the name:
     *
     *     var ed = Ext.create('User', {name: 'Ed Spencer'});
     *
     *     console.log(ed.get('firstName')); //logs 'Ed', based on our convert function
     *
     * Fields which are configured with a custom ```convert``` function are read *after* all other fields
     * when constructing and reading records, so that if convert functions rely on other, non-converted fields
     * (as in this example), they can be sure of those fields being present.
     *
     * In fact, if we log out all of the data inside ed, we'll see this:
     *
     *     console.log(ed.data);
     *
     *     //outputs this:
     *     {
     *         age: 0,
     *         email: "",
     *         firstName: "Ed",
     *         gender: "Unknown",
     *         name: "Ed Spencer"
     *     }
     *
     * The age field has been given a default of zero because we made it an int type. As an auto field, email has defaulted
     * to an empty string. When we registered the User model we set gender's {@link #defaultValue} to 'Unknown' so we see
     * that now. Let's correct that and satisfy ourselves that the types work as we expect:
     *
     *     ed.set('gender', 'Male');
     *     ed.get('gender'); //returns 'Male'
     *
     *     ed.set('age', 25.4);
     *     ed.get('age'); //returns 25 - we wanted an int, not a float, so no decimal places allowed
     */
    Ext.define('Ext.data.Field', {
        requires: ['Ext.data.Types', 'Ext.data.SortTypes'],
        alias: 'data.field',

        isField: true,

        constructor : function(config) {
            var me = this,
                types = Ext.data.Types,
                st;

            if (Ext.isString(config)) {
                config = {name: config};
            }
            Ext.apply(me, config);

            st = me.sortType;

            if (me.type) {
                if (Ext.isString(me.type)) {
                    me.type = types[me.type.toUpperCase()] || types.AUTO;
                }
            } else {
                me.type = types.AUTO;
            }

            // named sortTypes are supported, here we look them up
            if (Ext.isString(st)) {
                me.sortType = Ext.data.SortTypes[st];
            } else if(Ext.isEmpty(st)) {
                me.sortType = me.type.sortType;
            }

            // Reference this type's default converter if we did not recieve one in configuration.
            if (!config.hasOwnProperty('convert')) {
                me.convert = me.type.convert; // this may be undefined (e.g., AUTO)
            } else if (!me.convert && me.type.convert && !config.hasOwnProperty('defaultValue')) {
                // If the converter has been nulled out, and we have not been configured
                // with a field-specific defaultValue, then coerce the inherited defaultValue into our data type.
                me.defaultValue = me.type.convert(me.defaultValue);
            }

            if (config.convert) {
                me.hasCustomConvert = true;
            }
        },

        /**
         * @cfg {String} name
         *
         * The name by which the field is referenced within the Model. This is referenced by, for example, the `dataIndex`
         * property in column definition objects passed to {@link Ext.grid.property.HeaderContainer}.
         *
         * Note: In the simplest case, if no properties other than `name` are required, a field definition may consist of
         * just a String for the field name.
         */

        /**
         * @cfg {String/Object} type
         *
         * The data type for automatic conversion from received data to the *stored* value if
         * `{@link Ext.data.Field#convert convert}` has not been specified. This may be specified as a string value.
         * Possible values are
         *
         * - auto (Default, implies no conversion)
         * - string
         * - int
         * - float
         * - boolean
         * - date
         *
         * This may also be specified by referencing a member of the {@link Ext.data.Types} class.
         *
         * Developers may create their own application-specific data types by defining new members of the {@link
         * Ext.data.Types} class.
         */

        /**
         * @cfg {Function} [convert]
         *
         * A function which converts the value provided by the Reader into an object that will be stored in the Model.
         *
         * If configured as `null`, then no conversion will be applied to the raw data property when this Field
         * is read. This will increase performance. but you must ensure that the data is of the correct type and does
         * not *need* converting.
         *
         * It is passed the following parameters:
         *
         * - **v** : Mixed
         *
         *   The data value as read by the Reader, if undefined will use the configured `{@link Ext.data.Field#defaultValue
         *   defaultValue}`.
         *
         * - **rec** : Ext.data.Model
         *
         *   The data object containing the Model as read so far by the Reader. Note that the Model may not be fully populated
         *   at this point as the fields are read in the order that they are defined in your
         *   {@link Ext.data.Model#cfg-fields fields} array.
         *
         * Example of convert functions:
         *
         *     function fullName(v, record){
         *         return record.data.last + ', ' + record.data.first;
         *     }
         *
         *     function location(v, record){
         *         return !record.data.city ? '' : (record.data.city + ', ' + record.data.state);
         *     }
         *
         *     Ext.define('Dude', {
         *         extend: 'Ext.data.Model',
         *         fields: [
         *             {name: 'fullname',  convert: fullName},
         *             {name: 'firstname', mapping: 'name.first'},
         *             {name: 'lastname',  mapping: 'name.last'},
         *             {name: 'city', defaultValue: 'homeless'},
         *             'state',
         *             {name: 'location',  convert: location}
         *         ]
         *     });
         *
         *     // create the data store
         *     var store = Ext.create('Ext.data.Store', {
         *         reader: {
         *             type: 'json',
         *             model: 'Dude',
         *             idProperty: 'key',
         *             root: 'daRoot',
         *             totalProperty: 'total'
         *         }
         *     });
         *
         *     var myData = [
         *         { key: 1,
         *           name: { first: 'Fat',    last:  'Albert' }
         *           // notice no city, state provided in data object
         *         },
         *         { key: 2,
         *           name: { first: 'Barney', last:  'Rubble' },
         *           city: 'Bedrock', state: 'Stoneridge'
         *         },
         *         { key: 3,
         *           name: { first: 'Cliff',  last:  'Claven' },
         *           city: 'Boston',  state: 'MA'
         *         }
         *     ];
         */

        /**
         * @cfg {Function} [serialize]
         * A function which converts the Model's value for this Field into a form which can be used by whatever {@link Ext.data.writer.Writer Writer}
         * is being used to sync data with the server.
         *
         * The function should return a string which represents the Field's value.
         *
         * It is passed the following parameters:
         *
         * - **v** : Mixed
         *
         *   The Field's value - the value to be serialized.
         *
         * - **rec** : Ext.data.Model
         *
         *   The record being serialized.
         *
         */

        /**
         * @cfg {String} dateFormat
         *
         * Serves as a default for the {@link #dateReadFormat} and {@link #dateWriteFormat} config options. This
         * will be used in place of those other configurations if not specified.
         *
         * A format string for the {@link Ext.Date#parse Ext.Date.parse} function, or "timestamp" if the value provided by
         * the Reader is a UNIX timestamp, or "time" if the value provided by the Reader is a javascript millisecond
         * timestamp. See {@link Ext.Date}.
         *
         * It is quite important to note that while this config is optional, it will default to using the base
         * JavaScript Date object's `parse` function if not specified, rather than {@link Ext.Date#parse Ext.Date.parse}.
         * This can cause unexpected issues, especially when converting between timezones, or when converting dates that
         * do not have a timezone specified. The behavior of the native `Date.parse` is implementation-specific, and
         * depending on the value of the date string, it might return the UTC date or the local date. __For this reason
         * it is strongly recommended that you always specify an explicit date format when parsing dates.__
         */
        dateFormat: null,

        /**
         * @cfg {String} dateReadFormat
         * Used when converting received data into a Date when the {@link #type} is specified as `"date"`.
         * This configuration takes precedence over {@link #dateFormat}.
         * See {@link #dateFormat} for more information.
         */
        dateReadFormat: null,

        /**
         * @cfg {String} dateWriteFormat
         * Used to provide a custom format when serializing dates with a {@link Ext.data.writer.Writer}.
         * If this is not specified, the {@link #dateFormat} will be used. See the {@link Ext.data.writer.Writer}
         * docs for more information on writing dates.
         */
        dateWriteFormat: null,

        /**
         * @cfg {Boolean} useNull
         *
         * Use when converting received data into a INT, FLOAT, BOOL or STRING type. If the value cannot be
         * parsed, `null` will be used if useNull is true, otherwise a default value for that type will be used:
         *
         * - for INT and FLOAT - `0`.
         * - for STRING - `""`.
         * - for BOOL - `false`.
         *
         * Note that when parsing of DATE type fails, the value will be `null` regardless of this setting.
         */
        useNull: false,

        /**
         * @cfg {Object} [defaultValue=""]
         *
         * The default value used when the creating an instance from a raw data object, and the property referenced by the
         * `{@link Ext.data.Field#mapping mapping}` does not exist in that data object.
         *
         * May be specified as `undefined` to prevent defaulting in a value.
         */
        defaultValue: "",

        /**
         * @cfg {String/Number} mapping
         *
         * (Optional) A path expression for use by the {@link Ext.data.reader.Reader} implementation that is creating the
         * {@link Ext.data.Model Model} to extract the Field value from the data object. If the path expression is the same
         * as the field name, the mapping may be omitted.
         *
         * The form of the mapping expression depends on the Reader being used.
         *
         * - {@link Ext.data.reader.Json}
         *
         *   The mapping is a string containing the javascript expression to reference the data from an element of the data
         *   item's {@link Ext.data.reader.Json#cfg-root root} Array. Defaults to the field name.
         *
         * - {@link Ext.data.reader.Xml}
         *
         *   The mapping is an {@link Ext.DomQuery} path to the data item relative to the DOM element that represents the
         *   {@link Ext.data.reader.Xml#record record}. Defaults to the field name.
         *
         * - {@link Ext.data.reader.Array}
         *
         *   The mapping is a number indicating the Array index of the field's value. Defaults to the field specification's
         *   Array position.
         *
         * If a more complex value extraction strategy is required, then configure the Field with a {@link #convert}
         * function. This is passed the whole row object, and may interrogate it in whatever way is necessary in order to
         * return the desired data.
         */
        mapping: null,

        /**
         * @cfg {Function/String} sortType
         *
         * A function which converts a Field's value to a comparable value in order to ensure correct sort ordering.
         * Predefined functions are provided in {@link Ext.data.SortTypes}. A custom sort example:
         *
         *     // current sort     after sort we want
         *     // +-+------+          +-+------+
         *     // |1|First |          |1|First |
         *     // |2|Last  |          |3|Second|
         *     // |3|Second|          |2|Last  |
         *     // +-+------+          +-+------+
         *
         *     sortType: function(value) {
         *        switch (value.toLowerCase()) // native toLowerCase():
         *        {
         *           case 'first': return 1;
         *           case 'second': return 2;
         *           default: return 3;
         *        }
         *     }
         *
         * May also be set to a String value, corresponding to one of the named sort types in {@link Ext.data.SortTypes}.
         */
        sortType : null,

        /**
         * @cfg {String} sortDir
         *
         * Initial direction to sort (`"ASC"` or `"DESC"`). Defaults to `"ASC"`.
         */
        sortDir : "ASC",

        /**
         * @cfg {Boolean} allowBlank
         * @private
         *
         * Used for validating a {@link Ext.data.Model model}. Defaults to true. An empty value here will cause
         * {@link Ext.data.Model}.{@link Ext.data.Model#isValid isValid} to evaluate to false.
         */
        allowBlank : true,

        /**
         * @cfg {Boolean} persist
         *
         * False to exclude this field from the {@link Ext.data.Model#modified} fields in a model. This will also exclude
         * the field from being written using a {@link Ext.data.writer.Writer}. This option is useful when model fields are
         * used to keep state on the client but do not need to be persisted to the server. Defaults to true.
         */
        persist: true
    });