Parse Nested XML Objective C - NSXMLParser - iphone

Question

All,
I have XML in the following format:
<linked-list>
<Description>
<desc></desc>
<IP></IP>
</Description>
</linked-list>
This XML statement could have an infinite number of <Description></Description> inside of the <linked-list></linked-list>.
How should I parse this using NSXMLParser? My current code is as follows, but it parses incorrectly.
#implementation XMLParser
#synthesize response;
- (XMLParser *) initXMLParser
{
self = [super init];
// init dictionary of response data
response = [[NSMutableDictionary alloc] init];
return self;
}
//Gets Start Element of SessionData
- (void)parser:(NSXMLParser *)parser
didStartElement:(NSString *)elementName
namespaceURI:(NSString *)namespaceURI
qualifiedName:(NSString *)qualifiedName
attributes:(NSDictionary *)attributeDict
{
if ([elementName isEqualToString:#"linked-list"])
{
NSLog(#"Found linked-list in the return XML! Continuing...");
//response is a NSMutableArray instance variable
//THIS SHOULD NEVER NEED TO BE USED
if (!response)//if array is empty, it makes it!
{
NSLog(#"Dictionary is empty for some reason, creating...");
response = [[NSMutableDictionary alloc] init];
}
//END: THIS SHOULD NEVER BE USED
return;
}
else
{
currentElementName = elementName;
NSLog(#"Current Element Name = %#", currentElementName);
return;
}
}
- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
if (!currentElementValue) {
// init the ad hoc string with the value
currentElementValue = [[NSMutableString alloc] initWithString:string];
} else {
[currentElementValue setString:string];
NSLog(#"Processing value for : %#", string);
}
}
//Gets End Element of linked-list
- (void)parser:(NSXMLParser *)parser
didEndElement:(NSString *)elementName
namespaceURI:(NSString *)namespaceURI
qualifiedName:(NSString *)qName {
if ([elementName isEqualToString:#"linked-list"])
{
// We reached the end of the XML document
// dumps dictionary into log
NSLog(#"Dump:%#", [response description]);
return;
}
else
{
//Adds key and object to dictionary
[response setObject:currentElementValue forKey:currentElementName];
NSLog(#"Set values, going around again... brb.");
}
currentElementValue = nil;
currentElementName = nil;
}
#end

Answer 1

Some observations:
An infinite number of WHAT inside of the WHAT?
Assuming there can be more than one Description element, the outer data structure in which you store the contents must be a NSMutableArray, not a dictionary. You then use one mutable dictionary per Description element.
Consequently, in didStartElement:, check if the element name is #"Description" and if so, create a new NSMutableDictionary instance that you store in an ivar.
In foundCharacters:, you always have to append the new characters to the existing currentElementValue because the method can be called multiple times for each element's contents. I see many people do this wrong despite the fact that Apple's sample code clearly demonstrates the correct way.
In didEndElement:, do this:
If the element name is #"desc" or #"IP", assign currentElementValue to the corresponding key in your current mutable dictionary. Don't forget to release currentElementValue before you set it to nil. You currently have a memory leak in your code because you're not doing that.
If the element name is #"Description", add the current mutable dictionary to the mutable array. Release the dictionary and set the ivar to nil. A new dictionary will be created the next time you encounter a #"Description" element in didStartElement:.
If the element name is #"linked-list", the mutable array will contain all the dictionaries and you're done.