Question

I am using a NSXMLParserDelegate method to get the data from
XML file but I cant get the data I want.
The xml file is like:

<faces>
  <bounds x='70' y='250' width='438' height='438'/>
  <right-eye x='208' y='424'/>
  <left-eye x='368' y='426'/>
  <features s-avg='0.82' s-min='0.51' s-max='0.92'>
    <point id='PR' x='223' y='425' s='0.76'/>
    <point id='PL' x='362' y='424' s='0.91'/>
</faces>

From this file I want to get the values for attributes x,y, and s only for the point element with attribute id equal to "PR".
Logging the value should show x=223.

This is my parsing process:

-(void) parser:(NSXMLParser *) parser didStartElement:(NSString *) elementName namespaceURI:(NSString *) namespaceURI qualifiedName:(NSString *) qName attributes:(NSDictionary *) attributeDict {
  if ([elementName isEqualToString:@"point"]) 
  {
      NSString *idvalue = [attributeDict objectForKey:@"id"];
      if (idvalue==@"PR")
      {
          NSString *xvalue = [attributeDict objectForKey:@"x"];
          NSLog(@"%@",xvalue);
          NSString *yvalue = [attributeDict objectForKey:@"y"];
          NSLog(@"%@",yvalue);
          NSString *svalue = [attributeDict objectForKey:@"s"];
          NSLog(@"%@",svalue);   
      }
   }

I will get a log like:

X=223 X=362 Y=425 Y=424 S=0.76 S=0.91

Values of x,y,and s for all elements.
How can I get the values only for element with the attribute ID=”PR”?
I am hoping someone can give me a reason why or if you can point me in a direction to finally get this problem solved because its becoming a real pain in the behind.

Answer 1

Essentially, as Matthias pointed out in comments, you want to use NSString‘s -isEqualToString method. The reason for this is that idvalue==@"PR" is really just comparing the numeric value of the two NSString pointers, not their contents. The -isEqualToString method actually compares the contents of the strings referenced by said pointers.

Used as:

NSString *idvalue = [attributeDict objectForKey:@"id"];
if ([idvalue isEqualToString:@"PR"])
{
    NSString *xvalue = [attributeDict objectForKey:@"x"];
    NSLog(@"%@",xvalue);
    NSString *yvalue = [attributeDict objectForKey:@"y"];
    NSLog(@"%@",yvalue);
    NSString *svalue = [attributeDict objectForKey:@"s"];
    NSLog(@"%@",svalue);
}