ObjectAtIndex causes app to crash - iphone

Question

When I do an NSLog of the contents of my NSMutableArray, it returns :
(
hat,
hat
)
So why is it that when I do an NSLog like so NSLog(#"%#", [pro.matches objectAtIndex:0]); it crashes with the error: *** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 0 beyond bounds for empty array'
So strange
This is where I fill it:
[self.matches removeAllObjects];
NSArray *JSONarray = [[NSArray alloc] initWithArray:[NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:nil]];
int i;
for (i=0; i<[JSONarray count]; i++) {
//[self.matches addObject:[JSONarray objectAtIndex:i]];
[self.matches addObject:#"hat"];
}
//NSLog(#"boys with bo%#", [[matches objectAtIndex:1] objectForKey:#"host"]);
block();
//JSON and add to matches.
}
}];
block();
and this is where i call it:
[pro refreshMatchesWithCallback:^
{
//[self.tableView reloadData];
NSLog(#"the count of a lifetime is %#", [pro.matches objectAtIndex:0]);
}];

Answer 1

When you first log the contents it has nothing in due to the way completion blocks work, try this:
[pro refreshMatchesWithCallback:^
{
//[self.tableView reloadData];
if(pro.matches.count > 0) {
NSLog(#"the count of a lifetime is %#", [pro.matches objectAtIndex:0]);
}
}];
Hope this Helps!
Sam

Answer 2

always prefer to use this approach
for(Object* obj in arra)
{
...
}
this will enter in loop if the counter is greater than 0. no check needed
Cheerz :P