# Yahoo! UI Library

### base 3.1.1

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,
            build;

        Base._build = function(name, main, extensions, px, sx, cfg) {

            var build = Base._build,

                builtClass = build._ctor(main, cfg),
                buildCfg = build._cfg(main, cfg),

                _mixCust = build._mixCust,

                aggregates = buildCfg.aggregates,
                custom = buildCfg.custom,

                dynamic = builtClass._yuibuild.dynamic,

                i, l, val, extClass;

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

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

                // Prototype, old non-displacing augment
                Y.mix(builtClass, extClass, true, null, 1);
                 // Custom Statics
                _mixCust(builtClass, extClass, aggregates, custom);

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

            if (px) {
                Y.mix(builtClass.prototype, px, true);
            }

            if (sx) {
                Y.mix(builtClass, build._clean(sx, aggregates, custom), true);
                _mixCust(builtClass, sx, aggregates, custom);
            }

            builtClass.prototype.hasImpl = build._impl;

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

            return builtClass;
        };

        build = Base._build;

        Y.mix(build, {

            _mixCust: function(r, s, aggregates, custom) {

                if (aggregates) {
                    Y.aggregate(r, s, true, aggregates);
                }

                if (custom) {
                    for (var j in custom) {
                        if (custom.hasOwnProperty(j)) {
                            custom[j](j, r, s);
                        }
                    }
                }
            },

            _tmpl: function(main) {

                function BuiltClass() {
                    BuiltClass.superclass.constructor.apply(this, arguments);
                }
                Y.extend(BuiltClass, main);

                return BuiltClass;
            },

            _impl : function(extClass) {
                var classes = this._getClasses(), i, l, cls, exts, ll, j;
                for (i = 0, l = classes.length; i < l; i++) {
                    cls = classes[i];
                    if (cls._yuibuild) {
                        exts = cls._yuibuild.exts;
                        ll = exts.length;

                        for (j = 0; j < ll; j++) {
                            if (exts[j] === extClass) {
                                return true;
                            }
                        }
                    }
                }
                return false;
            },

            _ctor : function(main, cfg) {

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

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

                return builtClass;
            },

            _cfg : function(main, cfg) {
                var aggr = [],
                    cust = {},
                    buildCfg,
                    cfgAggr = (cfg && cfg.aggregates),
                    cfgCustBuild = (cfg && cfg.custom),
                    c = main;

                while (c && c.prototype) {
                    buildCfg = c._buildCfg;
                    if (buildCfg) {
                        if (buildCfg.aggregates) {
                            aggr = aggr.concat(buildCfg.aggregates);
                        }
                        if (buildCfg.custom) {
                            Y.mix(cust, buildCfg.custom, true);
                        }
                    }
                    c = c.superclass ? c.superclass.constructor : null;
                }

                if (cfgAggr) {
                    aggr = aggr.concat(cfgAggr);
                }
                if (cfgCustBuild) {
                    Y.mix(cust, cfg.cfgBuild, true);
                }

                return {
                    aggregates: aggr,
                    custom: cust
                };
            },

            _clean : function(sx, aggregates, custom) {
                var prop, i, l, sxclone = Y.merge(sx);

                for (prop in custom) {
                    if (sxclone.hasOwnProperty(prop)) {
                        delete sxclone[prop];
                    }
                }

                for (i = 0, l = aggregates.length; i < l; i++) {
                    prop = aggregates[i];
                    if (sxclone.hasOwnProperty(prop)) {
                        delete sxclone[prop];
                    }
                }

                return sxclone;
            }
        });

        /**
         * <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) {
            return build(name, main, extensions, null, null, cfg);
        };

        /**
         * <p>Creates a new class (constructor function) which extends the base class passed in as the second argument,
         * and mixes in the array of extensions provided.</p>
         * <p>Prototype properties or methods can be added to the new class, using the px argument (similar to Y.extend).</p>
         * <p>Static properties or methods can be added to the new class, using the sx argument (similar to Y.extend).</p>
         * <p>
         *
         * </p>
         * @method Base.create
         * @static
         * @param {Function} name The name of the newly created class. Used to defined the NAME property for the new class.
         * @param {Function} main The base class which the new class should extend. This class needs to be Base or a class derived from base (e.g. Widget).
         * @param {Function[]} extensions The list of extensions which will be mixed into the built class.
         * @return {Function} The newly created class.
         */
        Base.create = function(name, base, extensions, px, sx) {
            return build(name, base, extensions, px, sx);
        };

        /**
         * <p>Mixes in a list of extensions to an existing class.</p>
         * @method Base.mix
         * @static
         * @param {Function} main The existing class into which the extensions should be mixed.  The class needs to be Base or class derived from base (e.g. Widget)
         * @param {Function[]} extensions The set of extension classes which will mixed into the existing main class.
         * @return {Function} The modified main class, with extensions mixed in.
         */
        Base.mix = function(main, extensions) {
            return build(null, main, extensions, null, null, {dynamic:false});
        };

        /**
         * 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 = {
            custom : {
                ATTRS : function(prop, r, s) {
                    r[prop] = r[prop] || {};
                    if (s[prop]) {
                        Y.aggregate(r[prop], s[prop], true);
                    }
                }
            },
            aggregates : ["_PLUG", "_UNPLUG"]
        };

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