無法理解NSXMLParser

Question

我無法理解NSXMLParser。我嘗試了一些外部的XML解析器，但是我沒有運氣。我想要做的是解析GDATA Youtube API xml，它檢索視頻的xml。這工作正常，我有XML，但它很難通過元素重申。我只是需要一個例子，可以檢索元素，如（媒體：縮略圖URL =「」）（/媒體：縮略圖）

如何我從元素媒體的URL值：縮略圖

的網址我請求是https://gdata.youtube.com/feeds/api/videos?q=football+-soccer&orderby=published&start-index=11&max-results=10&v=2

Answer 1

這是你如何使用NSXMLParser：

在您的.h文件中聲明：

NSMutableData  *webPortFolio; 
NSMutableString  *soapResultsPortFolio; 
NSURLConnection  *conn; 

//---xml parsing--- 

NSXMLParser   *xmlParserPortFolio; 
BOOL    elementFoundPortFolio; 
NSMutableURLRequest *req; 

NSString   *theXMLPortFolio; 
NSString   *strSoapMsg; 
UIAlertView   *alertView; 

在您.m文件使用下面的代碼：

-(void)callURL 
{ 

    //Your logic to call URL. 

    conn = [[NSURLConnection alloc] initWithRequest:req delegate:self]; 
    if (conn) 
    { 
     webPortFolio = [[NSMutableData data] retain]; 
    } 
} 

，並處理您可以使用以下功能的響應：

-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response 
{ 
    [webPortFolio setLength:0];  
} 

-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data 
{ 
    [webPortFolio appendData:data]; 
} 

-(void) connection:(NSURLConnection *) connection didFailWithError:(NSError *) error 
{ 

    NSLog(@"error...................%@",[error description]); 
    [webPortFolio release]; 
    [connection release]; 
} 

-(void) connectionDidFinishLoading:(NSURLConnection *) connection 
{ 

    //Check the request and returns the response. 

    NSLog(@"DONE. Received Bytes: %d", [webPortFolio length]); 

    theXMLPortFolio = [[NSString alloc] 
         initWithBytes: [webPortFolio mutableBytes] 
         length:[webPortFolio length] 
         encoding:NSUTF8StringEncoding]; 

    //---shows the XML--- 

    NSLog(@"shows the XML %@",theXMLPortFolio); 
    [theXMLPortFolio release];  

    if(xmlParserPortFolio) 
    { 
     [xmlParserPortFolio release]; 
    } 
    xmlParserPortFolio = [[NSXMLParser alloc] initWithData: webPortFolio]; 
    [xmlParserPortFolio setDelegate: self]; 
    [xmlParserPortFolio setShouldResolveExternalEntities:YES]; 
    [xmlParserPortFolio parse]; 
    [webPortFolio release]; 
    [connection release]; 
} 

//---when the start of an element is found--- 
-(void) parser:(NSXMLParser *) parser 
didStartElement:(NSString *) elementName 
    namespaceURI:(NSString *) namespaceURI 
    qualifiedName:(NSString *) qName 
    attributes:(NSDictionary *) attributeDict 
{ 

    if([elementName isEqualToString:@"GetPortfolioListResult"]) 
    { 
     if (!soapResultsPortFolio) 
     { 
      soapResultsPortFolio = [[NSMutableString alloc] init]; 
     } 
     elementFoundPortFolio = TRUE; 
     NSLog(@"Registration...%@",soapResultsPortFolio); 
    } 
    else if([elementName isEqualToString:@"your_tag_name"]) 
    { 
     elementFoundPortFolio = TRUE; 
    } 
    else if([elementName isEqualToString:@"your_tag_name"]) 
    { 
     elementFoundPortFolio = TRUE; 
    } 
    else if([elementName isEqualToString:@"your_tag_name"]) 
    { 
     elementFoundPortFolio = TRUE; 
    } 

} 

-(void)parser:(NSXMLParser *) parser foundCharacters:(NSString *)string 
{ 
    if (elementFoundPortFolio) 
    { 
     [soapResultsPortFolio appendString: string]; 
    }  
} 

- (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError 
{ 
    NSLog(@"Parser error %@ ",[parseError description]); 
} 


//---when the end of element is found--- 
-(void)parser:(NSXMLParser *)parser 
didEndElement:(NSString *)elementName 
namespaceURI:(NSString *)namespaceURI 
qualifiedName:(NSString *)qName 
{ 
    if ([elementName isEqualToString:@"GetPortfolioListResult"]) 
    {   
     NSLog(@"display the soap results%@",soapResultsPortFolio); 
    } 
    else if([elementName isEqualToString:@"your_tag_name"]) 
    {   
     //Perform required action 
    } 
    else if([elementName isEqualToString:@"your_tag_name"]) 
    { 
     //Perform required action 
    } 
    else if([elementName isEqualToString:@"your_tag_name"]) 
    { 
     //Perform required action 
    } 

    [soapResultsPortFolio setString:@""]; 
    elementFoundPortFolio = FALSE; 
} 

編輯：

if ([elementName isEqualToString:@"media:thumbnail"]) 
{ 
     //Save your URL in an Array 
}