iPhone开发技巧之网络篇（1）— 解析XML

//DownloadOperation.h
#import<Foundation/Foundation.h>
#import<libxml/tree.h>
@interfaceDownloadOperation:NSOperation
{
NSURLRequest*_request;
NSURLConnection*_connection;
xmlParserCtxtPtr_parserContext;
BOOL_isExecuting,_isFinished;
BOOL_isChannel,_isItem;
NSMutableDictionary*_channel;
NSMutableDictionary*_currentItem;
NSMutableString*_currentCharacters;
}
//Property
@property(readonly)NSDictionary*channel;
//Initialize
-(id)initWithRequest:(NSURLRequest*)request;
@end

//DownloadOperation.m

#import"DownloadOperation.h"
@interfaceDownloadOperation(private)
-(void)startElementLocalName:(constxmlChar*)localname
prefix:(constxmlChar*)prefix
URI:(constxmlChar*)URI
nb_namespaces:(int)nb_namespaces
namespaces:(constxmlChar**)namespaces
nb_attributes:(int)nb_attributes
nb_defaulted:(int)nb_defaulted
attributes:(constxmlChar**)attributes;
-(void)endElementLocalName:(constxmlChar*)localname
prefix:(constxmlChar*)prefixURI:(constxmlChar*)URI;
-(void)charactersFound:(constxmlChar*)ch
len:(int)len;
@end
staticvoidstartElementHandler(
void*ctx,
constxmlChar*localname,
constxmlChar*prefix,
constxmlChar*URI,
intnb_namespaces,
constxmlChar**namespaces,
intnb_attributes,
intnb_defaulted,
constxmlChar**attributes)
{
[(DownloadOperation*)ctx
startElementLocalName:localname
prefix:prefixURI:URI
nb_namespaces:nb_namespaces
namespaces:namespaces
nb_attributes:nb_attributes
nb_defaulted:nb_defaulted
attributes:attributes];
}
staticvoidendElementHandler(
void*ctx,
constxmlChar*localname,
constxmlChar*prefix,
constxmlChar*URI)
{
[(DownloadOperation*)ctx
endElementLocalName:localname
prefix:prefix
URI:URI];
}
staticvoidcharactersFoundHandler(
void*ctx,
constxmlChar*ch,
intlen)
{
[(DownloadOperation*)ctx
charactersFound:chlen:len];
}
staticxmlSAXHandler_saxHandlerStruct={
NULL,/*internalSubset*/
NULL,/*isStandalone*/
NULL,/*hasInternalSubset*/
NULL,/*hasExternalSubset*/
NULL,/*resolveEntity*/
NULL,/*getEntity*/
NULL,/*entityDecl*/
NULL,/*notationDecl*/
NULL,/*attributeDecl*/
NULL,/*elementDecl*/
NULL,/*unparsedEntityDecl*/
NULL,/*setDocumentLocator*/
NULL,/*startDocument*/
NULL,/*endDocument*/
NULL,/*startElement*/
NULL,/*endElement*/
NULL,/*reference*/
charactersFoundHandler,/*characters*/
NULL,/*ignorableWhitespace*/
NULL,/*processingInstruction*/
NULL,/*comment*/
NULL,/*warning*/
NULL,/*error*/
NULL,/*fatalError//:unusederror()getalltheerrors*/
NULL,/*getParameterEntity*/
NULL,/*cdataBlock*/
NULL,/*externalSubset*/
XML_SAX2_MAGIC,/*initialized*/
NULL,/*private*/
startElementHandler,/*startElementNs*/
endElementHandler,/*endElementNs*/
NULL,/*serror*/
};
@implementationDownloadOperation
//Property
@synthesizechannel=_channel;
//--------------------------------------------------------------//
#pragmamark--Initialize--
//--------------------------------------------------------------//

+(BOOL)automaticallyNotifiesObserversForKey:(NSString*)key
{
if([keyisEqualToString:@"isExecuting"]||
[keyisEqualToString:@"isFinished"])
{
returnYES;
}
return[superautomaticallyNotifiesObserversForKey:key];
}
-(id)initWithRequest:(NSURLRequest*)request
{
if(![superinit]){
returnnil;
}
//实例初始化
_request=[requestretain];
_isExecuting=NO;
_isFinished=NO;
_channel=[[NSMutableDictionarydictionary]retain];
[_channelsetObject:[NSMutableArrayarray]forKey:@"items"];
_currentItem=nil;
returnself;
}
-(void)dealloc
{
//内存释放
[_requestrelease],_request=nil;
[_connectioncancel];
[_connectionrelease],_connection=nil;
[_channelrelease],_channel=nil;
[_currentCharactersrelease],_currentCharacters=nil;
[superdealloc];
}
//--------------------------------------------------------------//
#pragmamark--Operating--
//--------------------------------------------------------------//

-(BOOL)isConcurrent
{
returnYES;
}
-(BOOL)isExecuting
{
return_isExecuting;
}
-(BOOL)isFinished
{
return_isFinished;
}
-(void)start
{
//开始下载
if(![selfisCancelled]){
//创建XML解析器
_parserContext=xmlCreatePushParserCtxt(&_saxHandlerStruct,self,NULL,0,NULL);
//设定标志
[selfsetValue:[NSNumbernumberWithBool:YES]forKey:@"isExecuting"];
_isChannel=NO;
_isItem=NO;
//创建连接
[NSURLConnectionconnectionWithRequest:_requestdelegate:self];
}
}
-(void)cancel
{
//释放XML解析器
if(_parserContext){
xmlFreeParserCtxt(_parserContext),_parserContext=NULL;
}
[_connectioncancel],_connection=nil;
[selfsetValue:[NSNumbernumberWithBool:NO]forKey:@"isExecuting"];
[selfsetValue:[NSNumbernumberWithBool:YES]forKey:@"isFinished"];
[supercancel];
}
//--------------------------------------------------------------//
#pragmamark--NSURLConnectiondelegate--
//--------------------------------------------------------------//

-(void)connection:(NSURLConnection*)connection
didReceiveData:(NSData*)data
{
//添加解析数据
xmlParseChunk(_parserContext,(constchar*)[databytes],[datalength],0);
}
-(void)connectionDidFinishLoading:(NSURLConnection*)connection
{
//添加解析数据（结束）
xmlParseChunk(_parserContext,NULL,0,1);
//释放XML解析器
if(_parserContext){
xmlFreeParserCtxt(_parserContext),_parserContext=NULL;
}
//设定标志
_connection=nil;
[selfsetValue:[NSNumbernumberWithBool:NO]forKey:@"isExecuting"];
[selfsetValue:[NSNumbernumberWithBool:YES]forKey:@"isFinished"];
}
-(void)connection:(NSURLConnection*)connection
didFailWithError:(NSError*)error
{
//释放XML解析器
if(_parserContext){
xmlFreeParserCtxt(_parserContext),_parserContext=NULL;
}
//设定标志
_connection=nil;
[selfsetValue:[NSNumbernumberWithBool:NO]forKey:@"isExecuting"];
[selfsetValue:[NSNumbernumberWithBool:YES]forKey:@"isFinished"];
}
//--------------------------------------------------------------//
#pragmamark--libxmlhandler--
//--------------------------------------------------------------//

-(void)startElementLocalName:(constxmlChar*)localname
prefix:(constxmlChar*)prefix
URI:(constxmlChar*)URI
nb_namespaces:(int)nb_namespaces
namespaces:(constxmlChar**)namespaces
nb_attributes:(int)nb_attributes
nb_defaulted:(int)nb_defaulted
attributes:(constxmlChar**)attributes
{
//channel
if(strncmp((char*)localname,"channel",sizeof("channel"))==0){
_isChannel=YES;
return;
}
//item
if(strncmp((char*)localname,"item",sizeof("item"))==0){
_isItem=YES;
_currentItem=[NSMutableDictionarydictionary];
[[_channelobjectForKey:@"items"]addObject:_currentItem];
return;
}
//title,link,description
if(strncmp((char*)localname,"title",sizeof("title"))==0||
strncmp((char*)localname,"link",sizeof("link"))==0||
strncmp((char*)localname,"description",sizeof("description"))==0)
{
//创建字符串
[_currentCharactersrelease],_currentCharacters=nil;
_currentCharacters=[[NSMutableStringstring]retain];
}
}
-(void)endElementLocalName:(constxmlChar*)localname
prefix:(constxmlChar*)prefixURI:(constxmlChar*)URI
{
//channel
if(strncmp((char*)localname,"channel",sizeof("channel"))==0){
_isChannel=NO;
return;
}
//item
if(strncmp((char*)localname,"item",sizeof("item"))==0){
_isItem=NO;
_currentItem=nil;
return;
}
//title,link,description
if(strncmp((char*)localname,"title",sizeof("title"))==0||
strncmp((char*)localname,"link",sizeof("link"))==0||
strncmp((char*)localname,"description",sizeof("description"))==0)
{
NSString*key;
key=[NSStringstringWithCString:(char*)localnameencoding:NSUTF8StringEncoding];
NSMutableDictionary*dict=nil;
if(_isItem){
dict=_currentItem;
}
elseif(_isChannel){
dict=_channel;
}
[dictsetObject:_currentCharactersforKey:key];
[_currentCharactersrelease],_currentCharacters=nil;
}
}
-(void)charactersFound:(constxmlChar*)ch
len:(int)len
{
//添加解析到的字符串
if(_currentCharacters){
NSString*string;
string=[[NSStringalloc]initWithBytes:chlength:lenencoding:NSUTF8StringEncoding];
[_currentCharactersappendString:string];
[stringrelease];
}
}
@end