Question

I am trying to retrieve value for id:

{"id":1,"name":"XYZ"}

When I use:

NSString *jsonData = [[NSString alloc] initWithContentsOfURL:[NSURL URLWithString:url]];
NSArray * myPeople = [jsonData JSONValue]; 

NSString *name = [[NSString alloc] init]; 
NSDictionary *person = [myPeople objectAtIndex:[indexPath row]]; 
name = [NSString stringWithString:[person valueForKey:@"id"]]; 
name = [name stringByAppendingString:@". "]; 
name = [name stringByAppendingString:[person valueForKey:@"name"]]; 
name = [name stringByAppendingString:[person valueForKey:@"id"]]; 

cell.textLabel.text = name;

I get the following error:

*** Terminating app due to uncaught exception 'NSInvalidArgumentException'
reason: '-[NSCFNumber length]: unrecognized selector sent to instance 0x4e7f8b0

How can I fix this?

Answer 1

You are calling both stringWithString: and stringByAppendingString: but then passing in an NSNumber

You need to get the string value of the NSNumber

[[person valueForKey:@"id"] stringValue];

or use a format like:

name = [NSString stringWithFormat:@"%@%@", name, [person valueForKey:@"id"]];

I would also consider changing the structure slightly to make it easier to follow like this:

NSDictionary *person = [myPeople objectAtIndex:[indexPath row]];
NSString *personName = [person valueForKey:@"name"];
NSSNumber *personId  = [person valueForKey:@"id"];

NSString *name = [NSString stringWithFormat:@"%@. %@ %@", personId, personName, personId];

For sorting you want to make sure you are not pulling that data every time you set up a cell (looks like you are) or it will be a terrible experience.

I’m sure someone can point you to a better way of sorting but the quickest thing I can think of is

NSArray *myPeople = [[jsonData JSONValue] sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
  return [[obj1 objectForKey:@"id"] compare:[obj2 objectForKey:@"id"]];
}]