# Yahoo! UI Library

### datasource 3.0.0b1

Yahoo! UI Library > datasource > datasource-cache.js (source view)
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    /**
     * Extends DataSource with caching functionality.
     *
     * @module datasource
     * @submodule datasource-cache
     */

    /**
     * Adds cacheability to the DataSource Utility.
     * @class DataSourceCache
     * @extends Cache
     */
    var DataSourceCache = function() {
        DataSourceCache.superclass.constructor.apply(this, arguments);
    };

    Y.mix(DataSourceCache, {
        /**
         * The namespace for the plugin. This will be the property on the host which
         * references the plugin instance.
         *
         * @property NS
         * @type String
         * @static
         * @final
         * @value "cache"
         */
        NS: "cache",

        /**
         * Class name.
         *
         * @property NAME
         * @type String
         * @static
         * @final
         * @value "dataSourceCache"
         */
        NAME: "dataSourceCache",

        /////////////////////////////////////////////////////////////////////////////
        //
        // DataSourceCache Attributes
        //
        /////////////////////////////////////////////////////////////////////////////

        ATTRS: {

        }
    });

    Y.extend(DataSourceCache, Y.Cache, {
        /**
        * Internal init() handler.
        *
        * @method initializer
        * @param config {Object} Config object.
        * @private
        */
        initializer: function(config) {
            this.doBefore("_defRequestFn", this._beforeDefRequestFn);
            this.doBefore("_defResponseFn", this._beforeDefResponseFn);
        },

        /**
         * First look for cached response, then send request to live data.
         *
         * @method _beforeDefRequestFn
         * @param e {Event.Facade} Event Facade with the following properties:
         * <dl>
         * <dt>tId (Number)</dt> <dd>Unique transaction ID.</dd>
         * <dt>request (Object)</dt> <dd>The request.</dd>
         * <dt>callback (Object)</dt> <dd>The callback object.</dd>
         * <dt>cfg (Object)</dt> <dd>Configuration object.</dd>
         * </dl>
         * @protected
         */
        _beforeDefRequestFn: function(e) {
            // Is response already in the Cache?
            var entry = (this.retrieve(e.request)) || null;
            if(entry && entry.response) {
                this.get("host").fire("response", Y.mix({response: entry.response}, e));
                return new Y.Do.Halt("DataSourceCache plugin halted _defRequestFn");
            }
        },

        /**
         * Adds data to cache before returning data.
         *
         * @method _beforeDefResponseFn
         * @param e {Event.Facade} Event Facade with the following properties:
         * <dl>
         * <dt>tId (Number)</dt> <dd>Unique transaction ID.</dd>
         * <dt>request (Object)</dt> <dd>The request.</dd>
         * <dt>callback (Object)</dt> <dd>The callback object with the following properties:
         *     <dl>
         *         <dt>success (Function)</dt> <dd>Success handler.</dd>
         *         <dt>failure (Function)</dt> <dd>Failure handler.</dd>
         *     </dl>
         * </dd>
         * <dt>data (Object)</dt> <dd>Raw data.</dd>
         * <dt>response (Object)</dt> <dd>Normalized response object with the following properties:
         *     <dl>
         *         <dt>cached (Object)</dt> <dd>True when response is cached.</dd>
         *         <dt>results (Object)</dt> <dd>Parsed results.</dd>
         *         <dt>meta (Object)</dt> <dd>Parsed meta data.</dd>
         *         <dt>error (Object)</dt> <dd>Error object.</dd>
         *     </dl>
         * </dd>
         * <dt>cfg (Object)</dt> <dd>Configuration object.</dd>
         * </dl>
         * @protected
         */
         _beforeDefResponseFn: function(e) {
            // Add to Cache before returning
            if(e.response && !e.response.cached) {
                e.response.cached = true;
                this.add(e.request, e.response, (e.callback && e.callback.argument));
            }
         }
    });

    Y.namespace('Plugin').DataSourceCache = DataSourceCache;

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