    /**
     * @author Ed Spencer
     * @class Ext.data.Field
     * @extends Object
     *
     * <p>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:</p>
     *
    <pre><code>
    Ext.define('User', {
        extend: 'Ext.data.Model',
        fields: [
            'name', 'email',
            {name: 'age', type: 'int'},
            {name: 'gender', type: 'string', defaultValue: 'Unknown'}
        ]
    });
    </code></pre>
     *
     * <p>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:</p>
     *
    <pre><code>
    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'}
        ]
    });
    </code></pre>
     *
     * <p><u>Types and conversion</u></p>
     *
     * <p>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.</p>
     *
     * <p>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:</p>
     *
    <code><pre>
    Ext.define('User', {
        extend: 'Ext.data.Model',
        fields: [
            'name', 'email',
            {name: 'age', type: 'int'},
            {name: 'gender', type: 'string', defaultValue: 'Unknown'},

            {
                name: 'firstName',
                convert: function(value, record) {
                    var fullName  = record.get('name'),
                        splits    = fullName.split(" "),
                        firstName = splits[0];

                    return firstName;
                }
            }
        ]
    });
    </code></pre>
     *
     * <p>Now when we create a new User, the firstName is populated automatically based on the name:</p>
     *
    <code><pre>
    var ed = Ext.ModelManager.create({name: 'Ed Spencer'}, 'User');

    console.log(ed.get('firstName')); //logs 'Ed', based on our convert function
    </code></pre>
     *
     * <p>In fact, if we log out all of the data inside ed, we'll see this:</p>
     *
    <code><pre>
    console.log(ed.data);

    //outputs this:
    {
        age: 0,
        email: "",
        firstName: "Ed",
        gender: "Unknown",
        name: "Ed Spencer"
    }
    </code></pre>
     *
     * <p>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:</p>
     *
    <code><pre>
    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
    </code></pre>
     *
     */
    Ext.define('Ext.data.Field', {
        requires: ['Ext.data.Types', 'Ext.data.SortTypes'],
        alias: 'data.field',

        constructor : function(config) {
            if (Ext.isString(config)) {
                config = {name: config};
            }
            Ext.apply(this, config);

            var types = Ext.data.Types,
                st = this.sortType,
                t;

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

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

            if (!this.convert) {
                this.convert = this.type.convert;
            }
        },

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

        /**
         * @cfg {Mixed} type
         * (Optional) The data type for automatic conversion from received data to the <i>stored</i> value if <code>{@link Ext.data.Field#convert convert}</code>
         * has not been specified. This may be specified as a string value. Possible values are
         * <div class="mdetail-params"><ul>
         * <li>auto (Default, implies no conversion)</li>
         * <li>string</li>
         * <li>int</li>
         * <li>float</li>
         * <li>boolean</li>
         * <li>date</li></ul></div>
         * <p>This may also be specified by referencing a member of the {@link Ext.data.Types} class.</p>
         * <p>Developers may create their own application-specific data types by defining new members of the
         * {@link Ext.data.Types} class.</p>
         */

        /**
         * @cfg {Function} convert
         * (Optional) A function which converts the value provided by the Reader into an object that will be stored
         * in the Model. It is passed the following parameters:<div class="mdetail-params"><ul>
         * <li><b>v</b> : Mixed<div class="sub-desc">The data value as read by the Reader, if undefined will use
         * the configured <code>{@link Ext.data.Field#defaultValue defaultValue}</code>.</div></li>
         * <li><b>rec</b> : Ext.data.Model<div class="sub-desc">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 #fields} array.</div></li>
         * </ul></div>
         * <pre><code>
    // example of convert function
    function fullName(v, record){
        return record.name.last + ', ' + record.name.first;
    }

    function location(v, record){
        return !record.city ? '' : (record.city + ', ' + record.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 = new 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'
        }
    ];
         * </code></pre>
         */
        /**
         * @cfg {String} dateFormat
         * <p>(Optional) Used when converting received data into a Date when the {@link #type} is specified as <code>"date"</code>.</p>
         * <p>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}</p>
         */
        dateFormat: null,

        /**
         * @cfg {Boolean} useNull
         * <p>(Optional) Use when converting received data into a Number type (either int or float). If the value cannot be parsed,
         * null will be used if useNull is true, otherwise the value will be 0. Defaults to <tt>false</tt>
         */
        useNull: false,

        /**
         * @cfg {Mixed} defaultValue
         * (Optional) The default value used <b>when a Model is being created by a {@link Ext.data.reader.Reader Reader}</b>
         * when the item referenced by the <code>{@link Ext.data.Field#mapping mapping}</code> does not exist in the data
         * object (i.e. undefined). (defaults to "")
         */
        defaultValue: "",
        /**
         * @cfg {String/Number} mapping
         * <p>(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.</p>
         * <p>The form of the mapping expression depends on the Reader being used.</p>
         * <div class="mdetail-params"><ul>
         * <li>{@link Ext.data.reader.Json}<div class="sub-desc">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#root root} Array. Defaults to the field name.</div></li>
         * <li>{@link Ext.data.reader.Xml}<div class="sub-desc">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.</div></li>
         * <li>{@link Ext.data.reader.Array}<div class="sub-desc">The mapping is a number indicating the Array index
         * of the field's value. Defaults to the field specification's Array position.</div></li>
         * </ul></div>
         * <p>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.</p>
         */
        mapping: null,
        /**
         * @cfg {Function} sortType
         * (Optional) 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:<pre><code>
    // 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;
       }
    }
         * </code></pre>
         */
        sortType : null,
        /**
         * @cfg {String} sortDir
         * (Optional) Initial direction to sort (<code>"ASC"</code> or  <code>"DESC"</code>).  Defaults to
         * <code>"ASC"</code>.
         */
        sortDir : "ASC",
        /**
         * @cfg {Boolean} allowBlank
         * @private
         * (Optional) Used for validating a {@link Ext.data.Model model}, defaults to <code>true</code>.
         * An empty value here will cause {@link Ext.data.Model}.{@link Ext.data.Model#isValid isValid}
         * to evaluate to <code>false</code>.
         */
        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 <tt>true</tt>.
         */
        persist: true
    });