iOS XML,JOSN数据解析

解析:按照事先约好的格式提取数据的过程叫做解析

 后台开发人员按照约好的数据存入格式,前台按照约好的格式读取数据

iOS开发常⻅见的解析:XML解析、JSON解析 

XML解析:

主流格式:SAX, DOM(前台与后台都可以识别)

 XML解析的工作原理

 1.SAX:基于事件回调的解析机制,逐行进行解析,效率低,适合海量数据

 2.DOM:将解析的数据整体读入内存,初始化树形结构,逐行解析,效率高,适合于小量数据,谷歌提供了一个解析用的第三方,GDataXMLNode

//SAX解析

//1.找到.xml文件的路径
    NSString *filePath = [[NSBundle mainBundle] pathForResource:@"Student" ofType:@"xml"];
    //2.根据路径获取该路径下文件里的数据
    NSData *data = [NSData dataWithContentsOfFile:filePath];
    //3.进行SAX解析
    NSXMLParser *parser = [[NSXMLParser alloc] initWithData:data];
    //设置代理
    parser.delegate = self;
    //通知parser对象开始解析
    [parser parse];
    [parser release];

#pragma mark - NSXMLParserDelegate

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict{
    //如果判断走到Student的开始标签时创建一个Student对象
    if ([elementName isEqualToString:@"Student"]) {
        self.student = [[Student alloc] init];
        self.student.position = attributeDict[@"position"];
        
    }
//    NSLog(@"%@", attributeDict[@"position"]);
}

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string{
    self.value = string;
}

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName{
    if ([elementName isEqualToString:@"name"]) {
        self.student.name = self.value;
    }else if ([elementName isEqualToString:@"gender"]){
        self.student.gender = self.value;
    }else if ([elementName isEqualToString:@"motto"]){
        self.student.motto = self.value;
    }else if ([elementName isEqualToString:@"Student"]){
        [self.dataSource addObject:self.student];
    }
    
    
}

- (void)parserDidEndDocument:(NSXMLParser *)parser{
    [self.tableView reloadData];
    }

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return self.dataSource.count;
}


- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cell" forIndexPath:indexPath];
    
    // Configure the cell...
    Student *stu = self.dataSource[indexPath.row];
    cell.textLabel.text = [NSString stringWithFormat:@"%@ %@ %@ %@", stu.name, stu.gender, stu.motto, stu.position];
    return cell;
}

//DOM解析(两种方式1.从上往下找(从根节点往下寻找)2.直接找)

<span style="font-size:18px;">[self.dataSources removeAllObjects];
    NSString *filePath = [[NSBundle mainBundle] pathForResource:@"Student" ofType:@"xml"];
    //对象是error的时候要传取值符
    NSError *error = nil;
    NSString *string = [NSString stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:&error];
    //1.将数据整体存入内存
    GDataXMLDocument *document = [[[GDataXMLDocument alloc] initWithXMLString:string options:0 error:nil] autorelease];
    //2.找到根节点
    GDataXMLElement *rootElement = [document rootElement];
    //3.找student节点
    NSArray *studentElement = [rootElement elementsForName:@"Student"];
    //遍历获取到对应的叶子节点
    for (GDataXMLElement *obj in studentElement) {
        GDataXMLElement *nameElement = [[obj elementsForName:@"name"] firstObject];
        GDataXMLElement *genderElement =  [[obj elementsForName:@"gender"] firstObject];
        GDataXMLElement *mottoElement = [[obj elementsForName:@"motto"] firstObject];
        Student *student = [[[Student alloc] init] autorelease];
        //将叶子节点中的值赋给对应的对象
        student.name = [nameElement stringValue];
        student.gender = [genderElement stringValue];
        student.motto = [mottoElement stringValue];
        //获取节点中的标签值(属性值)
        GDataXMLNode *node = [obj attributeForName:@"position"];
        student.position = [node stringValue];
        [self.dataSources addObject:student];
    }
    [self.tableView reloadData];
</span>

2.DOM直接找

<span style="font-size:18px;">[self.dataSources removeAllObjects];
    NSString *filePath = [[NSBundle mainBundle] pathForResource:@"Student" ofType:@"xml"];
    //对象是error的时候要传取值符
    NSError *error = nil;
    NSString *string = [NSString stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:&error];
    //1.将数据整体存入内存
    GDataXMLDocument *document = [[[GDataXMLDocument alloc] initWithXMLString:string options:0 error:nil] autorelease];
    //2.直接通过相对路径找到叶子节点
    NSArray *stus = [document nodesForXPath:@"//Student" error:nil];
    NSArray *names = [document nodesForXPath:@"//name" error:nil];
    NSArray *genders = [document nodesForXPath:@"//gender" error:nil];
    NSArray *mottos = [document nodesForXPath:@"//motto" error:nil];
 //   NSArray *positions = [document nodesForXPath:@"//Student" error:nil];
    
    for (int i = 0; i < 3; i++) {
        //创建对象
        Student *stu = [[Student alloc] init];
        //取出对应的叶子节点
        GDataXMLElement *name = names[i];
        GDataXMLElement *gender = genders[i];
        GDataXMLElement *motto = mottos[i];
   //     GDataXMLElement *position = positions[i];
        GDataXMLElement *stuElement = stus[i];
        //给对象对应的属性赋值
        stu.name = [name stringValue];
        stu.gender = [gender stringValue];
        stu.motto = [motto stringValue];
        GDataXMLNode *node = [stuElement attributeForName:@"position"];
        stu.position = [node stringValue];
        //将对象放入数组
        [self.dataSources addObject:stu];
        [stu release];
    }
    [self.tableView reloadData];
}
</span>

JSON解析(简单,也是最常用的)

<span style="font-size:18px;">//1.找到.json文件的路径
    NSString *filePath = [[NSBundle mainBundle] pathForResource:@"Student" ofType:@"json"];
    //2.根据路径获取该路径下文件里的数据
    NSData *data = [NSData dataWithContentsOfFile:filePath];
    //3.解析
    NSError *error = nil;
    NSMutableArray *arr = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:&error];
//    NSLog(@"%@", arr);
    for (NSDictionary *dic in arr) {
        Student *stu = [[Student alloc] initWithDictionary:dic];
        [self.dataSourse addObject:stu];
    }
    [self.tableView reloadData];
</span>