Parsing an xml using NSXMLParser

mansi5 · 02-17-2010, 11:23 AM

Hi there!

I'm new to coding with Obj C and on the iPhone SDK. I'm having a little trouble understanding how NSXMLParser works. I used this NSXMLParser Simple Problem - Mac Forums as an example.

Basically I have an xml file that looks like this:

Code:

<?xml version="1.0" encoding="windows-1250"?>
<RootElement>
  <State>
    <Name>Arizona</Name>
    <Time>6 a.m.ñ2 a.m.</Time>
    <Time>6 a.m.</Time>
	<Notes>This is a note for Ar</Notes>
  </State>
  <State>
    <Name>California</Name>
    <Time>CA Time.</Time>
    <Time>CA Time2.</Time>
    <Notes>This is a note for California</Notes>
  </State>
</RootElement>

I'm trying to load this xml file from awakeAtNib, and load an NSMutableDictionary with key as name of each state, and value as an array containing all the values for time, time and notes.

When I actually do [xmlParser parse], nothing happens! Am I supposed to override the "parse" method somewhere?

Since it did not do anything, I explicitly called the two parser methods.
My delegate code looks like this:

Code:

//  XMLParserAppDelegate.m
//  XMLParser
//
//  Created by Mansi Gandhi on 2/16/10.
//  Copyright __MyCompanyName__ 2010. All rights reserved.
//

#import "XMLParserAppDelegate.h"

@implementation XMLParserAppDelegate

@synthesize window;


- (void)applicationDidFinishLaunching:(UIApplication *)application {    

    // Override point for customization after application launch
    [window makeKeyAndVisible];
}

- (void)awakeFromNib 
{
    NSLog(@"Awake from Nib");
	NSString *filePath = [[NSString stringWithString:@"~/Desktop/Sample.xml"]stringByStandardizingPath];
	[self parseXMLFile:filePath];
	
}
- (void)dealloc {
    [window release];
    [super dealloc];
}

- (void)parseXMLFile:(NSString *)pathToFile {
    BOOL success;
	
    NSURL *xmlURL = [NSURL fileURLWithPath:pathToFile];
    if (xmlParser) 
        [xmlParser release];
	
	xmlParser = [[NSXMLParser alloc] initWithContentsOfURL:xmlURL];
    [xmlParser setDelegate:self];
    [xmlParser setShouldResolveExternalEntities:YES];
    
	success = [xmlParser parse]; 
	[self parser:xmlParser didStartElement:@"RootElement"  attributes:dictionary];
	[self parser:xmlParser didEndElement:@"RootElement"];
	NSLog(@"End parsing!");
}

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName attributes:(NSDictionary *)attributeDict 
{
	
	if ( [elementName isEqualToString:@"RootElement"]) {
		NSLog(@"found rootelement");
		[self parser:xmlParser didStartElement:@"State"  attributes:dictionary];
		return;
    }
	
	if ( [elementName isEqualToString:@"State"] ) {
		NSLog(@"found state");
        return;
    }
	if ( [elementName isEqualToString:@"Name"] ) {
		NSLog(@"found name");
        return;
    }
	if ( [elementName isEqualToString:@"Time"] ) {
		NSLog(@"found time");
        return;
    }
	if ( [elementName isEqualToString:@"Notes"] ) {
		NSLog(@"found notes");
        return;
    }
	
}

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
	NSLog(@"found characters:%@",string);
        //Dont know what to do here!
}

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName  
{
	if ([elementName isEqualToString:@"RootElement"]) {
		NSLog(@"rootelement entering...");
	}
	if ([elementName isEqualToString:@"State"]) {
		NSLog(@"state entering...");
	}
	if ([elementName isEqualToString:@"Name"]) {
		NSLog(@"name entering...");
	}
	if ([elementName isEqualToString:@"Time"]) {
		NSLog(@"time entering...");
	}
	if ([elementName isEqualToString:@"Notes"]) {
		NSLog(@"notes entering...");
	}
}
@end

I don't know where I can get the value for that element. Like how do I get "CA Time." for <Time> under California, and then put it into a NSMutable Array.

Also, the way I call it obviously doesn't recurse for each state.

Any help is appreciated!

Thanks

Mansi

**smithdale87** · 02-17-2010, 12:22 PM

look at the NSXMLParserDelegate protocol methods.

You'll need to implement methods such as

Code:

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qualifiedName attributes:(NSDictionary *)attributeDict

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string

stuffradio · 02-17-2010, 01:05 PM

Like smithdale87 said, I have the following methods for iterating through the xml document.

Code:

- (void)parserDidStartDocument:(NSXMLParser *)parser
{
}

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName
  namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName
	attributes:(NSDictionary *)attributeDict
{
}

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string{
}

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName
  namespaceURI:(NSString *)namespaceURI
 qualifiedName:(NSString *)qName{
	
}

In didStartElement you initialize the items such as your dictionary, and any other variable you'll use to capture a string or any other value.

With foundCharacters, when it catches that value of the character it found, append the string to the variables.

When it gets to didEndElement, set the Object and give it a key then add the row to your dictionary.

Hope this helps!

mansi5 · 02-17-2010, 02:20 PM

Hi,

I get that the below methods are for NSXMLParserDelegate

Code:

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qualifiedName attributes:(NSDictionary *)attributeDict

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string

But when I set
[xmlParser setDelegate:self];
and then call
[xmlParser parse], is this supposed to call its delegate methods?

I mean, where are these delegate methods being called?

Sorry about my ingnorance

stuffradio · 02-17-2010, 02:48 PM

Quote:

Originally Posted by mansi5

Hi,

I get that the below methods are for NSXMLParserDelegate

Code:

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qualifiedName attributes:(NSDictionary *)attributeDict

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string

But when I set
[xmlParser setDelegate:self];
and then call
[xmlParser parse], is this supposed to call its delegate methods?

I mean, where are these delegate methods being called?

Sorry about my ingnorance

Yes, xmlParser parse does call the methods.

mansi5 · 02-17-2010, 03:55 PM

Quote:

Originally Posted by stuffradio

Yes, xmlParser parse does call the methods.

Oh, ok. Let me give it a shot then.
Thanks!

mansi5 · 02-17-2010, 10:16 PM

Quote:

Originally Posted by stuffradio

Yes, xmlParser parse does call the methods.

Hi,

I created a simple version of calling the delegate methods,

So now my .m file looks like:

Code:

//  XMLParserAppDelegate.m
//  XMLParser
//
//  Created by Mansi Gandhi on 2/16/10.
//  Copyright __MyCompanyName__ 2010. All rights reserved.
//

#import "XMLParserAppDelegate.h"

@implementation XMLParserAppDelegate

@synthesize window;


- (void)applicationDidFinishLaunching:(UIApplication *)application {    

    // Override point for customization after application launch
    [window makeKeyAndVisible];
}

- (void)awakeFromNib 
{
    NSLog(@"Awake from Nib");
	NSString *filePath = [[NSString stringWithString:@"~/Desktop/Sample.xml"]stringByStandardizingPath];
	[self parseXMLFile:filePath];
	
}
- (void)dealloc {
    [window release];
    [super dealloc];
}

- (void)parseXMLFile:(NSString *)pathToFile {
    BOOL success;
	
    NSURL *xmlURL = [NSURL fileURLWithPath:pathToFile];
    if (xmlParser) 
        [xmlParser release];
	
    xmlParser = [[NSXMLParser alloc] initWithContentsOfURL:xmlURL];
    [xmlParser setDelegate:self];
    
	success = [xmlParser parse]; 
	NSLog(@"End parsing!");
}

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qualifiedName attributes:(NSDictionary *)attributeDict
{
	NSLog(@"Did start element");
	if ( [elementName isEqualToString:@"RootElement"]) {
				NSLog(@"found rootElement");
			return;
		}
}

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName
{
	NSLog(@"Did end element");
	if ([elementName isEqualToString:@"RootElement"]) {
				NSLog(@"rootelement end");
		}
		
}
- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
	NSLog(@"Did fine characters");
}

But none of the log statements get printed => the delegate methods did not get called. Am I missing something?

Thanks again!

stuffradio · 02-17-2010, 10:45 PM

Quote:

Originally Posted by mansi5

Hi,

I created a simple version of calling the delegate methods,

So now my .m file looks like:

Code:

//  XMLParserAppDelegate.m
//  XMLParser
//
//  Created by Mansi Gandhi on 2/16/10.
//  Copyright __MyCompanyName__ 2010. All rights reserved.
//

#import "XMLParserAppDelegate.h"

@implementation XMLParserAppDelegate

@synthesize window;


- (void)applicationDidFinishLaunching:(UIApplication *)application {    

    // Override point for customization after application launch
    [window makeKeyAndVisible];
}

- (void)awakeFromNib 
{
    NSLog(@"Awake from Nib");
	NSString *filePath = [[NSString stringWithString:@"~/Desktop/Sample.xml"]stringByStandardizingPath];
	[self parseXMLFile:filePath];
	
}
- (void)dealloc {
    [window release];
    [super dealloc];
}

- (void)parseXMLFile:(NSString *)pathToFile {
    BOOL success;
	
    NSURL *xmlURL = [NSURL fileURLWithPath:pathToFile];
    if (xmlParser) 
        [xmlParser release];
	
    xmlParser = [[NSXMLParser alloc] initWithContentsOfURL:xmlURL];
    [xmlParser setDelegate:self];
    
	success = [xmlParser parse]; 
	NSLog(@"End parsing!");
}

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qualifiedName attributes:(NSDictionary *)attributeDict
{
	NSLog(@"Did start element");
	if ( [elementName isEqualToString:@"RootElement"]) {
				NSLog(@"found rootElement");
			return;
		}
}

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName
{
	NSLog(@"Did end element");
	if ([elementName isEqualToString:@"RootElement"]) {
				NSLog(@"rootelement end");
		}
		
}
- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
	NSLog(@"Did fine characters");
}

But none of the log statements get printed => the delegate methods did not get called. Am I missing something?

Thanks again!

You need to allocate an xmlParser and I don't think the simulator can read your hard drive, maybe I'm wrong though?

mansi5 · 02-19-2010, 08:10 PM

Quote:

Originally Posted by stuffradio

You need to allocate an xmlParser and I don't think the simulator can read your hard drive, maybe I'm wrong though?

Got it to work! Thanks so much

funkytaco · 02-20-2010, 09:44 AM

Quote:

Originally Posted by stuffradio

You need to allocate an xmlParser and I don't think the simulator can read your hard drive, maybe I'm wrong though?

Code:

- (XMLParser *) initXMLParser {
	
	[super init];
	
	appDelegate = ( MyAppDelegate *)[[UIApplication sharedApplication] delegate];
	
	return self;
}

I think that's what he was missing.

Aalok · 01-12-2012, 04:34 AM

Quote:

great tutorial
thanks for this