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>
<personid="1"> <firstName>Wythe</firstName>
<lastName>xu</lastName>
<age>22</age>
</person>
<personid="2">
<firstName>li</firstName>
<lastName>si</lastName>
<age>31</age>
</person>
<personid="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>@interfaceViewController : 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"@interfaceViewController ()@end@implementationViewController@synthesizeparser = _parser , person = _person , currenttag =_currenttag;- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self=[super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];if(self) {//Custom initialization}returnself;
}- (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.}#pragmamark 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:stringforKey:@"firstName"];
}if([_currenttag isEqualToString:@"lastName"] &&dict) {
[dict setObject:stringforKey:@"lastName"];
}if([_currenttag isEqualToString:@"age"] &&dict) {
[dict setObject:stringforKey:@"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。
2014-09-1016:45:32.920xmlforblog[3820:60b] start parse12014-09-1016:45:32.921xmlforblog[3820:60b] start element2014-09-1016:45:32.922xmlforblog[3820:60b] found characters2014-09-1016:45:32.922xmlforblog[3820:60b] start element2014-09-1016:45:32.922xmlforblog[3820:60b] found characters2014-09-1016:45:32.922xmlforblog[3820:60b] start element2014-09-1016:45:32.923xmlforblog[3820:60b] found characters2014-09-1016:45:32.923xmlforblog[3820:60b] end element2014-09-1016:45:32.923xmlforblog[3820:60b] found characters2014-09-1016:45:32.923xmlforblog[3820:60b] start element2014-09-1016:45:32.924xmlforblog[3820:60b] found characters2014-09-1016:45:32.924xmlforblog[3820:60b] end element2014-09-1016:45:32.924xmlforblog[3820:60b] found characters2014-09-1016:45:32.924xmlforblog[3820:60b] start element2014-09-1016:45:32.925xmlforblog[3820:60b] found characters2014-09-1016:45:32.925xmlforblog[3820:60b] end element2014-09-1016:45:32.925xmlforblog[3820:60b] found characters2014-09-1016:45:32.925xmlforblog[3820:60b] end element2014-09-1016:45:32.926xmlforblog[3820:60b] found characters2014-09-1016:45:32.926xmlforblog[3820:60b] start element2014-09-1016:45:32.928xmlforblog[3820:60b] found characters2014-09-1016:45:32.929xmlforblog[3820:60b] start element2014-09-1016:45:32.929xmlforblog[3820:60b] found characters2014-09-1016:45:32.929xmlforblog[3820:60b] end element2014-09-1016:45:32.930xmlforblog[3820:60b] found characters2014-09-1016:45:32.930xmlforblog[3820:60b] start element2014-09-1016:45:32.930xmlforblog[3820:60b] found characters2014-09-1016:45:32.930xmlforblog[3820:60b] end element2014-09-1016:45:32.931xmlforblog[3820:60b] found characters2014-09-1016:45:32.931xmlforblog[3820:60b] start element2014-09-1016:45:32.931xmlforblog[3820:60b] found characters2014-09-1016:45:32.931xmlforblog[3820:60b] end element2014-09-1016:45:32.931xmlforblog[3820:60b] found characters2014-09-1016:45:32.932xmlforblog[3820:60b] end element2014-09-1016:45:32.932xmlforblog[3820:60b] found characters2014-09-1016:45:32.932xmlforblog[3820:60b] start element2014-09-1016:45:32.932xmlforblog[3820:60b] found characters2014-09-1016:45:32.933xmlforblog[3820:60b] start element2014-09-1016:45:32.933xmlforblog[3820:60b] found characters2014-09-1016:45:32.933xmlforblog[3820:60b] end element2014-09-1016:45:32.933xmlforblog[3820:60b] found characters2014-09-1016:45:32.934xmlforblog[3820:60b] start element2014-09-1016:45:32.934xmlforblog[3820:60b] found characters2014-09-1016:45:32.934xmlforblog[3820:60b] end element2014-09-1016:45:32.934xmlforblog[3820:60b] found characters2014-09-1016:45:32.935xmlforblog[3820:60b] start element2014-09-1016:45:32.935xmlforblog[3820:60b] found characters2014-09-1016:45:32.935xmlforblog[3820:60b] end element2014-09-1016:45:32.935xmlforblog[3820:60b] found characters2014-09-1016:45:32.936xmlforblog[3820:60b] end element2014-09-1016:45:32.936xmlforblog[3820:60b] found characters2014-09-1016:45:32.936xmlforblog[3820:60b] end element2014-09-1016:45:32.936xmlforblog[3820:60b] parse end2014-09-1016:45:32.936xmlforblog[3820:60b] (
{
age=22;
firstName=Wythe;id=1;
lastName=xu;
},
{
age=31;
firstName=li;id=2;
lastName=si;
},
{
age=24;
firstName=Dipen;id=3;
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:stringforKey:@"firstName"];
}if([_currenttag isEqualToString:@"lastName"] &&dict) {
[dict setObject:stringforKey:@"lastName"];
}if([_currenttag isEqualToString:@"age"] &&dict) {
[dict setObject:stringforKey:@"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