前段时间想找点事做，就是试着看能不能用豆瓣的API做点什么，于是就碰到了这个问题——XML解析。
老师还没讲，只能自己去查。
XML文档解析主要有SAX和DOM两种模式，IOS上两种模式都可以用，这里就不做过多介绍，我选择的SAX模式。
IOS解析XML用的是自带的NSXML框架，框架的核心是NSXMLParser类和它的委托协议NSXMLParserDelegate，其主要的解析工作是在NSXMLParserDelegate实现类中完成的。委托中定义了许多回掉方法，在SAX解析器从上到下遍历XML文档的过程中，遇到开始标签、结束标签、文档开始、文档结束和字符串结束是就会触发这些方法。这些方法有很多，下面我们列出5个常用的方法。
在文档开始时触发
-(void)parserDidStartDocument:(NSXMLParser *)parser
遇到一个新标签是触发，其中namespaceURI是命名空间，qualifiedName是限定名，attributes是字典类型的属性集合。
-(void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict
找到字符串时触发
-(void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
遇到结束标签时触发
-(void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName
在文档结束时触发
-(void)parserDidEndDocument:(NSXMLParser *)parser
下面通过一个具体的例子来看整个的调用与解析过程
首先这是我们将要解析的XML文件 "info.xml"
<?xml version="1.0" encoding="UTF-8"?>
<root>
<person id="1">
<firstName>Wythe</firstName>
<lastName>xu</lastName>
<age>22</age>
</person>
<person id="2">
<firstName>li</firstName>
<lastName>si</lastName>
<age>31</age>
</person>
<person id="3">
<firstName>Dipen</firstName>
<lastName>Shah</lastName>
<age>24</age>
</person>
</root>
接来来是一个头文件 "ViewController.h"
#import <UIKit/UIKit.h> @interface ViewController : UIViewController<NSXMLParserDelegate> @property NSXMLParser *parser;
@property NSMutableArray *person;
@property NSString *currenttag; @end
然后是它的实现文件 "ViewController.m"
#import "ViewController.h" @interface ViewController () @end @implementation ViewController @synthesize parser = _parser , person = _person , currenttag = _currenttag; - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
} - (void)viewDidLoad
{
[super viewDidLoad]; NSString *xmlFilePath = [[NSBundle mainBundle]pathForResource:@"info"ofType:@"xml"]; NSData *data = [[NSData alloc]initWithContentsOfFile:xmlFilePath]; self.parser = [[NSXMLParser alloc]initWithData:data]; self.parser.delegate = self; [self.parser parse]; NSLog(@"%@",_person); } - (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
} #pragma mark delegate method -(void)parserDidStartDocument:(NSXMLParser *)parser
{
_person = [[NSMutableArray alloc]init];
NSLog(@"start parse 1");
} -(void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict
{
_currenttag = elementName; if ([_currenttag isEqualToString:@"person"]) {
NSString *_id = [attributeDict objectForKey:@"id"];
NSMutableDictionary *dict = [[NSMutableDictionary alloc]init];
[dict setObject:_id forKey:@"id"];
[_person addObject:dict];
} NSLog(@"start element");
} -(void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
NSMutableDictionary *dict = [_person lastObject]; if ([_currenttag isEqualToString:@"firstName"] && dict) {
[dict setObject:string forKey:@"firstName"]; }
if ([_currenttag isEqualToString:@"lastName"] && dict) {
[dict setObject:string forKey:@"lastName"];
}
if ([_currenttag isEqualToString:@"age"] && dict) {
[dict setObject:string forKey:@"age"];
} NSLog(@"found characters");
} -(void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName
{
_currenttag = nil; NSLog(@"end element");
} -(void)parserDidEndDocument:(NSXMLParser *)parser
{
NSLog(@"parse end");
}
@end
通过断电和输出信息，我们可以知道整个解析过程是 开始解析文档、开始标签、找到字符串、结束标签、文档结束。
-- ::32.920 xmlforblog[:60b] start parse
-- ::32.921 xmlforblog[:60b] start element
-- ::32.922 xmlforblog[:60b] found characters
-- ::32.922 xmlforblog[:60b] start element
-- ::32.922 xmlforblog[:60b] found characters
-- ::32.922 xmlforblog[:60b] start element
-- ::32.923 xmlforblog[:60b] found characters
-- ::32.923 xmlforblog[:60b] end element
-- ::32.923 xmlforblog[:60b] found characters
-- ::32.923 xmlforblog[:60b] start element
-- ::32.924 xmlforblog[:60b] found characters
-- ::32.924 xmlforblog[:60b] end element
-- ::32.924 xmlforblog[:60b] found characters
-- ::32.924 xmlforblog[:60b] start element
-- ::32.925 xmlforblog[:60b] found characters
-- ::32.925 xmlforblog[:60b] end element
-- ::32.925 xmlforblog[:60b] found characters
-- ::32.925 xmlforblog[:60b] end element
-- ::32.926 xmlforblog[:60b] found characters
-- ::32.926 xmlforblog[:60b] start element
-- ::32.928 xmlforblog[:60b] found characters
-- ::32.929 xmlforblog[:60b] start element
-- ::32.929 xmlforblog[:60b] found characters
-- ::32.929 xmlforblog[:60b] end element
-- ::32.930 xmlforblog[:60b] found characters
-- ::32.930 xmlforblog[:60b] start element
-- ::32.930 xmlforblog[:60b] found characters
-- ::32.930 xmlforblog[:60b] end element
-- ::32.931 xmlforblog[:60b] found characters
-- ::32.931 xmlforblog[:60b] start element
-- ::32.931 xmlforblog[:60b] found characters
-- ::32.931 xmlforblog[:60b] end element
-- ::32.931 xmlforblog[:60b] found characters
-- ::32.932 xmlforblog[:60b] end element
-- ::32.932 xmlforblog[:60b] found characters
-- ::32.932 xmlforblog[:60b] start element
-- ::32.932 xmlforblog[:60b] found characters
-- ::32.933 xmlforblog[:60b] start element
-- ::32.933 xmlforblog[:60b] found characters
-- ::32.933 xmlforblog[:60b] end element
-- ::32.933 xmlforblog[:60b] found characters
-- ::32.934 xmlforblog[:60b] start element
-- ::32.934 xmlforblog[:60b] found characters
-- ::32.934 xmlforblog[:60b] end element
-- ::32.934 xmlforblog[:60b] found characters
-- ::32.935 xmlforblog[:60b] start element
-- ::32.935 xmlforblog[:60b] found characters
-- ::32.935 xmlforblog[:60b] end element
-- ::32.935 xmlforblog[:60b] found characters
-- ::32.936 xmlforblog[:60b] end element
-- ::32.936 xmlforblog[:60b] found characters
-- ::32.936 xmlforblog[:60b] end element
-- ::32.936 xmlforblog[:60b] parse end
-- ::32.936 xmlforblog[:60b] (
{
age = ;
firstName = Wythe;
id = ;
lastName = xu;
},
{
age = ;
firstName = li;
id = ;
lastName = si;
},
{
age = ;
firstName = Dipen;
id = ;
lastName = Shah;
}
)
执行结果
而我们的处理主要是在 开始标签、找到字符串 （
-(void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict
-(void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
） 中。
遇到开始标签时，我们现判断标签，名字，如果是person，表明接下来就是person的信息，这样我们就先创建一个可变字典，以便将来存放它的值。
-(void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict
{
_currenttag = elementName; if ([_currenttag isEqualToString:@"person"]) {
NSString *_id = [attributeDict objectForKey:@"id"];
NSMutableDictionary *dict = [[NSMutableDictionary alloc]init];
[dict setObject:_id forKey:@"id"];
[_person addObject:dict];
} NSLog(@"start element");
}
在找到字符串时，我们就是通过判断当前标签名，将对应的信息保存到刚刚创建的字典中
-(void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
NSMutableDictionary *dict = [_person lastObject]; if ([_currenttag isEqualToString:@"firstName"] && dict) {
[dict setObject:string forKey:@"firstName"]; }
if ([_currenttag isEqualToString:@"lastName"] && dict) {
[dict setObject:string forKey:@"lastName"];
}
if ([_currenttag isEqualToString:@"age"] && dict) {
[dict setObject:string forKey:@"age"];
} NSLog(@"found characters");
}
不断循环这样的过程，最后我们就可以解析出整个XML文档。
另外说一句，这只是解析一般的文档，如果你跟我曾经一样学会这个就去解析豆瓣API的XML文档，会发现行不通。这时因为许多网站因为它的数据较多，为了避免标签的重复，使用了命名空间，带有命名空间的XML文档解析和这稍有不同。
以后我会写带命名空间的XML文档解析，敬请期待。
拖了快一个月了，今天终于写完。以后不能这么懒了