How to do selective parsing with NSXMLParser - objective-c

Question

I have the following XML:
<data>
<title>Bookstore</title>
<site>www.bookstore.com</site>
<lastUpdate>11/17/2011</lastUpdate>
<books>
<unit>
<title>
Beginning iPhone 4 Development: Exploring the iOS SDK
</title>
<author>David Mark, Jack Nutting, Jeff LaMarche</author>
<isbn10>143023024X</isbn10>
<isbn13>978-1430230243</isbn13>
<pubDate>January 28, 2011</pubDate>
<price>23.99</price>
<description>
Beginning iPhone 4 Development is a complete course in iOS development. You'll master techniques that work on iPhone, iPad, and iPod touch. We start with the basics showing you how to download and install the tools you'll need, and how to create your first simple application. Next you'll learn to integrate all the interface elements iOS users have come to know and love, such as buttons, switches, pickers, toolbars, and sliders.
</description>
</unit>
<unit>...</unit>
<unit>...</unit>
</books>
<clothes>
<unit>
<title>T-Shirt</title>
<size>M</size>
<color>Red</color>
<price>10.99</price>
<description>
100% cotton T-shirt, wash in cold water with like colors
</description>
</unit>
<unit>...</unit>
<unit>...</unit>
<unit>...</unit>
</clothes>
<accessories>
<unit>
<title>Mug - Large</title>
<color>Black</color>
<price>6.99</price>
<description>
Large 16-ounce ceramic coffee mug, with witty use of IIT name on it.
</description>
</unit>
<unit>...</unit>
</accessories>
</data>
This is the code I've got. I am checking if the tag encountered is "books".
- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName
namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qualifiedName
attributes:(NSDictionary *)attributeDict {
if([elementName isEqualToString:#"books"]) {
appDelegate.books = [[NSMutableArray alloc] init];
}
else if([elementName isEqualToString:#"unit"]) {
aBook = [[Book alloc] init];
}
NSLog(#"Processing Element: %#", elementName);
}
.
- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string {
if(!currentElementValue)
currentElementValue = [[NSMutableString alloc] initWithString:string];
else
[currentElementValue appendString:string];
NSLog(#"Processing Value: %#", currentElementValue);
}
Here I am trying to assign the values in each tag to a variable in the Book object.
- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName
namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName {
if (qName) {
elementName = qName;
}
if (aBook) {
if ([elementName isEqualToString:#"title"]) {
aBook.title = currentElementValue;
} else if ([elementName isEqualToString:#"author"]) {
aBook.author = currentElementValue;
} else if ([elementName isEqualToString:#"isbn10"]) {
aBook.isbn10 = currentElementValue;
} else if ([elementName isEqualToString:#"isbn13"]) {
aBook.isbn13 = currentElementValue;
} else if ([elementName isEqualToString:#"pubDate"]) {
aBook.pubDate = currentElementValue;
} else if ([elementName isEqualToString:#"price"]) {
aBook.price = currentElementValue;
} else if ([elementName isEqualToString:#"description"]) {
aBook.description = currentElementValue;
}
[appDelegate.books addObject:aBook];
[aBook release];
aBook = nil;
}
[currentElementValue release];
currentElementValue = nil;
}
I have a UITableView to display a the list of books,
Book *aBook = [appDelegate.books objectAtIndex:indexPath.row];
[[cell textLabel] setText:[aBook title]];
The problem is all the items are displayed in the table view, not just books. How do I limit the items displayed to be just from books. I think I'm going wrong in Parser DidStartElement method.
Thanks.

Answer 1

In parser:didEndElement:namespaceURI:qualifiedName: you need to check for the </books> tag, and ignore any <unit> tag after that.
One way to do that would be to use self.books instead of appDelegate.books inside your parser, and then only when you reach the </books> tag set appDelegate.books to self.books and then set self.books to nil. If you reach a <unit> tag and self.books is nil, then you ignore than unit.