How add a default value to an array when child element is not found in xml parsing?

Question

I am new to iphone development.I am parsing an XML page and displaying the content in a tableview.In some block in the XML page , the child element is missing , i want to add a value o in my array, when the child element is not fond in the particular block.My XML file is like

 <entry>
 <id>xxx </id>
 <title>xxxxx</title>
 <gd:ratings numRaters="2"/>
 </entry> ..................................>first block
 <entry>
 <id>xxx </id>
 <title>xxxxx</title>
 </entry> ....................................>Second block
 <entry>
 <id>xxx </id>
 <title>xxxxx</title>
 <gd:ratings numRaters="2"/>
 </entry> .....................................>Third block

I am parsing the gd:ratings tag and display its attribute numRates value in a tableview. I am having an mutable array which stores the value of numRates.I have to add object "O" in the array when the second block is parsed because it doesnot contain gd:ratings tag.Since the value is present in a attribute tag, for retrieving the content and adding it to the mutable array is done in NSXML parser DidStartElement method.

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

currentElement = [elementName copy];
if ([elementName isEqualToString:@"entry"]) {

    entry = [[NSMutableDictionary alloc] init];
    currentTitle = [[NSMutableString alloc] init];
    currentDate = [[NSMutableString alloc] init];
    NSLog(@"inside image1 ");
}else if([elementName isEqualToString:@"media:thumbnail"])
    { currentImage = [[NSMutableString alloc] init];
        if(myUrl == nil){   
        myUrl = [NSString stringWithString:[attributeDict objectForKey:@"url"]];
        }
        [currentImage appendString:myUrl];  
        [stories1 addObject:currentImage];
        myUrl=nil;
        }   else if([elementName isEqualToString:@"gd:rating"])
{
    currentRating=[[NSMutableString alloc]init];

        myRatings=[NSString stringWithString:[attributeDict objectForKey:@"numRaters"]];

    [currentRating appendString:myRatings];
    [stories2 addObject:currentRating];
}   
}

Since there are 25 blocks of entry tags and in that 10 block doesnot have gd rating element .So the array stories2 array has only 15 values.So i cannot display it in the tableview in order.Is there any way out to retrieve the attribute tag in "found characters" method . Please help me out.Thanks.

Answer 1

You can use the didEndElement method: when the outer element ended, check if the child element was added to the array.

You could use an iVar BOOL entryHasRating and do the following:

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

   currentElement = [elementName copy];
   if ([elementName isEqualToString:@"entry"]) {
     entryHasRating = NO;
     ...
   } else if ([elementName isEqualToString:@"gd:rating"]){
     entryHasRating = YES;
     ...
   }
}

Then when an element ends:

- (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName {
   if ([elementName isEqualToString:@"entry"]&& !entryHasRating) {
       [stories2 addObject:@"No Rating"];
       entryHasRating = YES; 
   }
   ...
}

Answer 2

If you know all of the data fields that you'll be expecting, you could build a dictionary with placeholders for all of your expected values before you parse the XML; as you parse the XML just replace the placeholders with real values.