//1.加载和解析XML文件
    NSString *path = [[NSBundle mainBundle] pathForResource:@"xml.txt" ofType:nil];
    NSData *data = [[NSData alloc] initWithContentsOfFile:path];
    // GDataXMLDocument 表示XML文档对象
    // initWithData 使用NSData初始化, 就是解析
    GDataXMLDocument *doc = [[GDataXMLDocument alloc] initWithData:data options:0 error:nil];
    
    //2.获取指定结点 XPath
    //CityName路径: /root/systemConfig/CityName
    NSArray *array = [doc nodesForXPath:@"/root/systemConfig/CityName" error:nil];
    //CityName
    GDataXMLElement *element = [array firstObject];
    NSLog(@"name=%@ value=%@",element.name,element.stringValue);
    
    //3.获取指定结点的属性
    NSArray *items = [doc nodesForXPath:@"/root/systemConfig/ComeChannel/Item" error:nil];
    GDataXMLElement *item = [items firstObject];
    //获取属性, 属性使用GDataXMLElement表示
    for(GDataXMLElement *attr  in item.attributes)
    {
        NSLog(@"a-name=%@ avalue=%@",attr.name,attr.stringValue);
    }
    
    
    //4.获取所有指定名字的结点(不管位置)
    //XPath语法: //Item
    NSArray *allItem = [doc nodesForXPath:@"//Item" error:nil];
    for (GDataXMLElement *e in allItem) {
        NSLog(@"name = %@",e.name);
    }
    
    //5.获取所有指定名字的属性(不管哪个结点的)
    //XPath语法: //@value
    NSArray *allValue = [doc nodesForXPath:@"//@value" error:nil];
    for (GDataXMLElement *e in allValue) {
        NSLog(@"value = %@",e.stringValue);
    }
    
    //6.逐层遍历XML文件
    //获取根节点
    GDataXMLElement *root = doc.rootElement;
    //获取子节点
    //root.children
    //获取子节点个数
    //root.childCount
    //获取指定名字的子节点
    //root elementsForName:<#(NSString *)#>
}