# Yahoo! UI Library

### dataschema 3.1.1

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, // unnecessary variables
                    data_out = {results:[],meta:{}};

                if(xmldoc && xmldoc.nodeType && (9 === xmldoc.nodeType || 1 === xmldoc.nodeType || 11 === xmldoc.nodeType) && 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 {
                    result = SchemaXML._getXPathResult(locator, context, xmldoc);
                    while(res = result.iterateNext()) {
                        value = res.textContent || res.value || res.text || res.innerHTML || null;
                    }

                    return Y.DataSchema.Base.parse(value, field);
                }
                catch(e) {
                    Y.log('SchemaXML._getLocationValue failed: ' + e.message);
                }

                return null;
            },

            /**
             * Fetches the XPath-specified result for a given location in an XML node or document.
             *
             * @param locator {String} The XPath location.
             * @param context {Object} XML node or document to search within.
             * @param xmldoc {Object} XML document to resolve namespace.
             * @return {Object} Data collection or null.
             * @static
             * @protected
             */
            _getXPathResult: function(locator, context, xmldoc) {
                // Standards mode
                if (! LANG.isUndefined(xmldoc.evaluate)) {
                    return xmldoc.evaluate(locator, context, xmldoc.createNSResolver(context.ownerDocument ? context.ownerDocument.documentElement : context.documentElement), 0, null);
                }
                // IE mode
                else {
                    var values=[], locatorArray = locator.split(/\b\/\b/), i=0, l=locatorArray.length, location, subloc, m, isNth;

                    // XPath is supported
                    try {
                        // this fixes the IE 5.5+ issue where childnode selectors begin at 0 instead of 1
                        xmldoc.setProperty("SelectionLanguage", "XPath");
                        values = context.selectNodes(locator);
                    }
                    // Fallback for DOM nodes and fragments
                    catch (e) {
                        // Iterate over each locator piece
                        for (; i<l && context; i++) {
                            location = locatorArray[i];

                            // grab nth child []
                            if ((location.indexOf("[") > -1) && (location.indexOf("]") > -1)) {
                                subloc = location.slice(location.indexOf("[")+1, location.indexOf("]"));
                                //XPath is 1-based while DOM is 0-based
                                subloc--;
                                context = context.childNodes[subloc];
                                isNth = true;
                            }
                            // grab attribute value @
                            else if (location.indexOf("@") > -1) {
                                subloc = location.substr(location.indexOf("@"));
                                context = subloc ? context.getAttribute(subloc.replace('@', '')) : context;
                            }
                            // grab that last instance of tagName
                            else if (-1 < location.indexOf("//")) {
                                subloc = context.getElementsByTagName(location.substr(2));
                                context = subloc.length ? subloc[subloc.length - 1] : null;
                            }
                            // find the last matching location in children
                            else if (l != i + 1) {
                                for (m=context.childNodes.length-1; 0 <= m; m-=1) {
                                    if (location === context.childNodes[m].tagName) {
                                        context = context.childNodes[m];
                                        m = -1;
                                    }
                                }
                            }
                        }

                        if (context) {
                            // attribute
                            if (LANG.isString(context)) {
                                values[0] = {value: context};
                            }
                            // nth child
                            else if (isNth) {
                                values[0] = {value: context.innerHTML};
                            }
                            // all children
                            else {
                                values = Y.Array(context.childNodes, 0, true);
                            }
                        }
                    }

                    // returning a mock-standard object for IE
                    return {
                        index: 0,

                        iterateNext: function() {
                            if (this.index >= this.values.length) {return undefined;}
                            var result = this.values[this.index];
                            this.index += 1;
                            return result;
                        },

                        values: values
                    };
                }
            },

            /**
             * Schema-parsed result field.
             *
             * @method _parseField
             * @param field {String | Object} Required. Field definition.
             * @param result {Object} Required. Schema parsed data object.
             * @param context {Object} Required. XML node or document to search within.
             * @static
             * @protected
             */
            _parseField: function(field, result, context) {
                if (field.schema) {
                    result[field.key] = SchemaXML._parseResults(field.schema, context, {results:[],meta:{}}).results;
                }
                else {
                    result[field.key || field] = SchemaXML._getLocationValue(field, context);
                }
            },

            /**
             * 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 result to add to results list.
             *
             * @method _parseResult
             * @param fields {Array} Required. A collection of field definition.
             * @param context {Object} Required. XML node or document to search within.
             * @return {Object} Schema-parsed data.
             * @static
             * @protected
             */
            _parseResult: function(fields, context) {
                var result = {}, j;

                // Find each field value
                for (j=fields.length-1; 0 <= j; j--) {
                    SchemaXML._parseField(fields[j], result, context);
                }

                return result;
            },

            /**
             * Schema-parsed list of results from full data
             *
             * @method _parseResults
             * @param schema {Object} Schema to parse against.
             * @param context {Object} XML node document parse.
             * @param data_out {Object} In-progress schema-parsed data to update.
             * @return {Object} Schema-parsed data.
             * @static
             * @protected
             */
            _parseResults: function(schema, context, data_out) {
                if (schema.resultListLocator && LANG.isArray(schema.resultFields)) {
                    var xmldoc = context.ownerDocument || context,
                        fields = schema.resultFields,
                        results = [],
                        node, result, nodeList, i=0;

                    if (schema.resultListLocator.match(/^[:\-\w]+$/)) {
                        nodeList = context.getElementsByTagName(schema.resultListLocator);

                        // loop through each result node
                        for (i=nodeList.length-1; 0 <= i; i--) {
                            results[i] = SchemaXML._parseResult(fields, nodeList[i]);
                        }
                    }
                    else {
                        nodeList = SchemaXML._getXPathResult(schema.resultListLocator, context, xmldoc);

                        // loop through the nodelist
                        while (node = nodeList.iterateNext()) {
                            results[i] = SchemaXML._parseResult(fields, node);
                            i += 1;
                        }
                    }

                    if (results.length) {
                        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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