Question

I have the following very simple XML returned from a webserver which I use ASIHttpRequest to connect to:

<element1>something</element1>
<element2>somethingelse</element2>
<element3>anotherthing</element3>

ASIHttpRequest can return it as NSData or NSString. I need to parse the information, what is the easiest way to do so?

Thanks

Answer 1

There are some XML parsers available for iOS NSXMLParser, libxml2 (DOM and SAX),TBXML,KissXML. You can refer http://www.raywenderlich.com/553/how-to-chose-the-best-xml-parser-for-your-iphone-project to choose best XML Parser (Speed and memory footprint). Easiest would be TBXML. NSXMLParser is easy as well.

NSXMLParser* xmlParser = [[NSXMLParser alloc] initWithData:receivedXMLData];//init NSXMLParser with receivedXMLData
[xmlParser setDelegate:self]; // Set delegate for NSXMLParser
[xmlParser parse]; //Start parsing
[xmlParser release];

//Delegate Methods
//Have a instance variable NSMutableString* currentString; to hold data between elements and NSMutableArray* elementsArray; to hold parsed data

- (void)parserDidStartDocument:(NSXMLParser *)parser
{
    elementsArray = [[NSMutableArray alloc] init];
}

//store all found characters between elements in currentString mutable string
- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
    if(!currentString)
    {
        currentString = [[NSMutableString alloc] init];
    }
    [currentString appendString:string];    
}

//When end of XML tag is found this method gets notified
- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName
{
    if([elementName isEqualToString:@"element1"])
    {
        [elementsArray addObject:currentString];
        [currentString release],currentString=nil;
        return;
    }
    if([elementName isEqualToString:@"element2"])
    {
        [elementsArray addObject:currentString];
        [currentString release],currentString=nil;
        return;
    }
    if([elementName isEqualToString:@"element3"])
    {
        [elementsArray addObject:currentString];
        [currentString release],currentString=nil;
        return;
    }
    [currentString release],currentString =nil;
}

//Parsing has ended
- (void)parserDidEndDocument:(NSXMLParser *)parser
{
    NSLog(@"Content of Elements Array: %@",elementsArray);
        [elementsArray release],elementsArray=nil;
}

- (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError
{
    UIAlertView* parseErrorAlert = [[UIAlertView alloc] initWithTitle:@"Parse Error" message:[NString stringWithFormat:"%@",[parseError localizedDescription]] delegate:nil cancelButtonTitle:@"Ok" otherButtonTitles:nil];
    [parseErrorAlert show];
    [parseErrorAlert release];
}

You have other delegate methods too like parseErrorOccured. Refer http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSXMLParser_Class/Reference/Reference.html

For TBXML : http://tbxml.co.uk/TBXML/API.html
Updated: Implemented parseError delegate method and valid xml example
XML You posted in code is not a valid XML (You can check XML validation online: http://validator.w3.org/#validate_by_input) so it will throw an parseError. Here is valid XML for XML you posted in question:

<?xml version="1.0"?>
<root>
 <element1>something</element1>
 <element2>somethingelse</element2>
 <element3>anotherthing</element3>
</root>