# Yahoo! UI Library

### dataschema 3.0.0b1

Yahoo! UI Library > dataschema > dataschema-xml.js (source view)
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    /**
     * Provides a DataSchema implementation which can be used to work with XML data.
     *
     * @module dataschema
     * @submodule dataschema-xml
     */
    var LANG = Y.Lang,

        /**
         * XML subclass for the DataSchema Utility.
         * @class DataSchema.XML
         * @extends DataSchema.Base
         * @static
         */
        SchemaXML = {

            /////////////////////////////////////////////////////////////////////////////
            //
            // DataSchema.XML static methods
            //
            /////////////////////////////////////////////////////////////////////////////
            /**
             * Applies a given schema to given XML data.
             *
             * @method apply
             * @param schema {Object} Schema to apply.
             * @param data {XMLDoc} XML document.
             * @return {Object} Schema-parsed data.
             * @static
             */
            apply: function(schema, data) {
                var xmldoc = data,
                    data_out = {results:[],meta:{}};

                if(xmldoc && xmldoc.nodeType && xmldoc.nodeType === 9 && schema) {
                    // Parse results data
                    data_out = SchemaXML._parseResults(schema, xmldoc, data_out);

                    // Parse meta data
                    data_out = SchemaXML._parseMeta(schema.metaFields, xmldoc, data_out);
                }
                else {
                    Y.log("XML data could not be schema-parsed: " + Y.dump(data) + " " + Y.dump(data), "error", "dataschema-xml");
                    data_out.error = new Error("XML schema parse failure");
                }

                return data_out;
            },

            /**
             * Get an XPath-specified value for a given field from an XML node or document.
             *
             * @method _getLocationValue
             * @param field {String | Object} Field definition.
             * @param context {Object} XML node or document to search within.
             * @return {Object} Data value or null.
             * @static
             * @protected
             */
            _getLocationValue: function(field, context) {
                var locator = field.locator || field.key || field,
                    xmldoc = context.ownerDocument || context,
                    result, res, value = null;

                try {
                    // Standards mode
                    if(!LANG.isUndefined(xmldoc.evaluate)) {
                        result = xmldoc.evaluate(locator, context, xmldoc.createNSResolver(!context.ownerDocument ? context.documentElement : context.ownerDocument.documentElement), 0, null);
                        while(res = result.iterateNext()) {
                            value = res.textContent;
                        }
                    }
                    // IE mode
                    else {
                        xmldoc.setProperty("SelectionLanguage", "XPath");
                        result = context.selectNodes(locator)[0];
                        value = result.value || result.text || null;
                    }
                    return Y.DataSchema.Base.parse(value, field);

                }
                catch(e) {
                }
            },

            /**
             * Parses results data according to schema
             *
             * @method _parseMeta
             * @param xmldoc_in {Object} XML document parse.
             * @param data_out {Object} In-progress schema-parsed data to update.
             * @return {Object} Schema-parsed data.
             * @static
             * @protected
             */
            _parseMeta: function(metaFields, xmldoc_in, data_out) {
                if(LANG.isObject(metaFields)) {
                    var key,
                        xmldoc = xmldoc_in.ownerDocument || xmldoc_in;

                    for(key in metaFields) {
                        if (metaFields.hasOwnProperty(key)) {
                            data_out.meta[key] = SchemaXML._getLocationValue(metaFields[key], xmldoc);
                        }
                    }
                }
                return data_out;
            },

            /**
             * Schema-parsed list of results from full data
             *
             * @method _parseResults
             * @param schema {Object} Schema to parse against.
             * @param xmldoc_in {Object} XML document parse.
             * @param data_out {Object} In-progress schema-parsed data to update.
             * @return {Object} Schema-parsed data.
             * @static
             * @protected
             */
            _parseResults: function(schema, xmldoc_in, data_out) {
                if(schema.resultListLocator && LANG.isArray(schema.resultFields)) {
                    var nodeList = xmldoc_in.getElementsByTagName(schema.resultListLocator),
                        fields = schema.resultFields,
                        results = [],
                        node, field, result, i, j;

                    if(nodeList.length) {
                        // Loop through each result node
                        for(i=nodeList.length-1; i>= 0; i--) {
                            result = {};
                            node = nodeList[i];

                            // Find each field value
                            for(j=fields.length-1; j>= 0; j--) {
                                field = fields[j];
                                result[field.key || field] = SchemaXML._getLocationValue(field, node);
                            }
                            results[i] = result;
                        }

                        data_out.results = results;
                    }
                    else {
                        data_out.error = new Error("XML schema result nodes retrieval failure");
                    }
                }
                return data_out;
            }
        };

    Y.DataSchema.XML = Y.mix(SchemaXML, Y.DataSchema.Base);

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