Question

I am having a strange problem when using this XML-to-NSDictionary class.really it was working great.
suddenly we found one weired problem using this.Let me explain this…when i have only one item the app is crashing. but when i have more than one item the app is not crashing.

When i have only one item to parse , after parsing if i print the count it shows as 6

But when i have more than one item, after parsing when i print the count it shows correctly

**

crash log:-
-[NSCFString objectAtIndex:]: unrecognized selector sent to instance
0x5c9a040 Terminating app due to
uncaught exception
‘NSInvalidArgumentException’, reason:
‘-[NSCFString objectAtIndex:]:
unrecognized selector sent to instance
0x5c9a040’

**

Please help me out and thanks for your time

Source code

-(void)RequestUpdate
    {
      NSDictionary *mailDict = [[XMLReader dictionaryForXMLString:responseXML error:nil] 

      valueForKeyPath:@"response.mails.mail"];

      NSLog(@"MAILS>MAIL COUNT %d %@", [mailDict count], mailDict);
    }

---

#import "XMLReader.h"

NSString *const kXMLReaderTextNodeKey = @"text";

@interface XMLReader (Internal)

- (id)initWithError:(NSError **)error;
- (NSDictionary *)objectWithData:(NSData *)data;

@end

---

@implementation XMLReader

#pragma mark -
#pragma mark Public methods

+ (NSDictionary *)dictionaryForXMLData:(NSData *)data error:(NSError **)error
{
    XMLReader *reader = [[XMLReader alloc] initWithError:error];
    NSDictionary *rootDictionary = [reader objectWithData:data];
    [reader release];
    return rootDictionary;
}

+ (NSDictionary *)dictionaryForXMLString:(NSString *)string error:(NSError **)error
{
    NSData *data = [string dataUsingEncoding:NSUTF8StringEncoding];
    return [XMLReader dictionaryForXMLData:data error:error];
}

#pragma mark -
#pragma mark Parsing

- (id)initWithError:(NSError **)error
{
    if ((self = [super init]))
    {
        errorPointer = error;
    }
    return self;
}

- (void)dealloc
{
    [dictionaryStack release];
    [textInProgress release];
    [super dealloc];
}

- (NSDictionary *)objectWithData:(NSData *)data
{
    // Clear out any old data
    [dictionaryStack release];
    [textInProgress release];

    dictionaryStack = [[NSMutableArray alloc] init];
    textInProgress = [[NSMutableString alloc] init];

    // Initialize the stack with a fresh dictionary
    [dictionaryStack addObject:[NSMutableDictionary dictionary]];

    // Parse the XML
    NSXMLParser *parser = [[[NSXMLParser alloc] initWithData:data] autorelease];
    parser.delegate = self;
    BOOL success = [parser parse];

    // Return the stack's root dictionary on success
    if (success)
    {
        NSDictionary *resultDict = [dictionaryStack objectAtIndex:0];
        return resultDict;
    }

    return nil;
}

#pragma mark -
#pragma mark NSXMLParserDelegate methods

- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict
{
    // Get the dictionary for the current level in the stack
    NSMutableDictionary *parentDict = [dictionaryStack lastObject];

    // Create the child dictionary for the new element, and initilaize it with the attributes
    NSMutableDictionary *childDict = [NSMutableDictionary dictionary];
    [childDict addEntriesFromDictionary:attributeDict];

    // If there's already an item for this key, it means we need to create an array
    id existingValue = [parentDict objectForKey:elementName];
    if (existingValue)
    {
        NSMutableArray *array = nil;
        if ([existingValue isKindOfClass:[NSMutableArray class]])
        {
            // The array exists, so use it
            array = (NSMutableArray *) existingValue;
        }
        else
        {
            // Create an array if it doesn't exist
            array = [NSMutableArray array];
            [array addObject:existingValue];

            // Replace the child dictionary with an array of children dictionaries
            [parentDict setObject:array forKey:elementName];
        }

        // Add the new child dictionary to the array
        [array addObject:childDict];
    }
    else
    {
        // No existing value, so update the dictionary
        [parentDict setObject:childDict forKey:elementName];
    }

    // Update the stack
    [dictionaryStack addObject:childDict];
}

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName
{
    // Update the parent dict with text info
    NSMutableDictionary *dictInProgress = [dictionaryStack lastObject];

    // Set the text property
    if ([textInProgress length] > 0)
    {
        [dictInProgress setObject:textInProgress forKey:kXMLReaderTextNodeKey];

        // Reset the text
        [textInProgress release];
        textInProgress = [[NSMutableString alloc] init];
    }

    // Pop the current dict
    [dictionaryStack removeLastObject];
}

- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string
{
    // Build the text value
    [textInProgress appendString:string];
}

- (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError
{
    // Set the error pointer to the parser's error object
    *errorPointer = parseError;
}

@end

---

Sample XML Data

<response>
  <mails>
    <mail id="4e12a3b04ff5ae0774000082">
      <created_on>2011-07-05T05:40:00+00:00</created_on>
      <updated_on>2011-07-05T05:40:00+00:00</updated_on>
      <creator id="4e0abdff54b53058ff0000a2"><name>Merk Warn</name></creator>
      <text>eee</text>
    </mail>
    <mail id="4e12dcvxva3b04ff5ae0774000082">
      <created_on>2011-07-05T05:40:00+00:00</created_on>
      <updated_on>2011-07-05T05:40:00+00:00</updated_on>
      <creator id="4e0abdff54b53058ff0000a2"><name>Merk Warn</name></creator>
      <text>eee</text>
    </mail>
 </mails>
</response>

Answer 1

That’s because the tag is stored directly as an NSDictionary object if there is only one element. The count you are getting is the number of key-value pairs in a dictionary.

You can handle this differently,

-(void)update
{
    id value = [[XMLReader dictionaryForXMLString:responseXML error:nil] valueForKeyPath:@"response.mails.mail"];

    NSArray * mails;
    if ( [value isKindOfClass:[NSDictionary class]] ) {
        mails = [NSArray arrayWithObject:value];
    }
    else {
        mails = (NSArray *)value;
    }

    /* `mails` is an array of <mail> based dictionaries */
}

You will have to retain it appropriately.