# Yahoo! UI Library

### base 3.0.0b1

Yahoo! UI Library > base > BaseBuild.js (source view)
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        /**
         * The base-build submodule provides Base.build functionality, which
         * can be used to create custom classes, by aggregating extensions onto
         * a main class.
         *
         * @module base
         * @submodule base-build
         * @for Base
         */

        var Base = Y.Base,
            L = Y.Lang;

        /**
         * The build configuration for the Base class.
         *
         * Defines the static fields which need to be aggregated
         * when the Base class is used as the main class passed to
         * the <a href="#method_Base.build">Base.build</a> method.
         *
         * @property Base._buildCfg
         * @type Object
         * @static
         * @final
         * @private
         */
        Base._buildCfg = {
            aggregates : ["ATTRS", "_PLUG", "_UNPLUG"]
        };

        /**
         * <p>
         * Builds a custom constructor function (class) from the
         * main function, and array of extension functions (classes)
         * provided. The NAME field for the constructor function is
         * defined by the first argument passed in.
         * </p>
         * <p>
         * The cfg object supports the following properties
         * </p>
         * <dl>
         *    <dt>dynamic &#60;boolean&#62;</dt>
         *    <dd>
         *    <p>If true (default), a completely new class
         *    is created which extends the main class, and acts as the
         *    host on which the extension classes are augmented.</p>
         *    <p>If false, the extensions classes are augmented directly to
         *    the main class, modifying the main class' prototype.</p>
         *    </dd>
         *    <dt>aggregates &#60;String[]&#62;</dt>
         *    <dd>An array of static property names, which will get aggregated
         *    on to the built class, in addition to the default properties build
         *    will always aggregate as defined by the main class' static _buildCfg
         *    property.
         *    </dd>
         * </dl>
         *
         * @method Base.build
         * @static
         * @param {Function} name The name of the new class. Used to defined the NAME property for the new class.
         * @param {Function} main The main class on which to base the built class
         * @param {Function[]} extensions The set of extension classes which will be
         * augmented/aggregated to the built class.
         * @param {Object} cfg Optional. Build configuration for the class (see description).
         * @return {Function} A custom class, created from the provided main and extension classes
         */
        Base.build = function(name, main, extensions, cfg) {

            var build = Base.build,
                builtClass = build._getClass(main, cfg),
                aggregates = build._getAggregates(main, cfg),
                dynamic = builtClass._yuibuild.dynamic,
                i, l, val, extClass;

            // Shallow isolate aggregates
            if (dynamic) {
                if (aggregates) {
                    for (i = 0, l = aggregates.length; i < l; ++i) {
                        val = aggregates[i];
                        if (main.hasOwnProperty(val)) {
                            builtClass[val] = L.isArray(main[val]) ? [] : {};
                        }
                    }
                    Y.aggregate(builtClass, main, true, aggregates);
                }
            }

            // Augment/Aggregate
            for (i = 0, l = extensions.length; i < l; i++) {
                extClass = extensions[i];

                if (aggregates) {
                    Y.aggregate(builtClass, extClass, true, aggregates);
                }

                // Old augment
                Y.mix(builtClass, extClass, true, null, 1);

                builtClass._yuibuild.exts.push(extClass);
            }

            builtClass.prototype.hasImpl = build._hasImpl;

            if (dynamic) {
                builtClass.NAME = name;
                builtClass.prototype.constructor = builtClass;
            }

            return builtClass;
        };

        Y.mix(Base.build, {

            _template: function(main) {

                function BuiltClass() {

                    BuiltClass.superclass.constructor.apply(this, arguments);

                    var f = BuiltClass._yuibuild.exts,
                        l = f.length,
                        i;

                    for (i = 0; i < l; i++) {
                        f[i].apply(this, arguments);
                    }

                    return this;
                }
                Y.extend(BuiltClass, main);

                return BuiltClass;
            },

            _hasImpl : function(extClass) {
                if (this.constructor._yuibuild) {
                    var f = this.constructor._yuibuild.exts,
                        l = f.length,
                        i;

                    for (i = 0; i < l; i++) {
                        if (f[i] === extClass) {
                            return true;
                        }
                    }
                }
                return false;
            },

            _getClass : function(main, cfg) {

               var dynamic = (cfg && false === cfg.dynamic) ? false : true,
                    builtClass = (dynamic) ? Base.build._template(main) : main;

                builtClass._yuibuild = {
                    id: null,
                    exts : [],
                    dynamic : dynamic
                };

                return builtClass;
            },

            _getAggregates : function(main, cfg) {
                var aggr = [],
                    cfgAggr = (cfg && cfg.aggregates),
                    c = main,
                    classAggr;

                while (c && c.prototype) {
                    classAggr = c._buildCfg && c._buildCfg.aggregates;
                    if (classAggr) {
                        aggr = aggr.concat(classAggr);
                    }
                    c = c.superclass ? c.superclass.constructor : null;
                }

                if (cfgAggr) {
                    aggr = aggr.concat(cfgAggr);
                }

                return aggr;
            }
        });

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