Why can I not identify simple string key values in a database (core data)

I am a newbie so I apologise if I am missing something obvious.

I am trying to write an app in Xcode 4 to produce stats for my local sports team.

This is the relevant detail of the problem area of my programme:

NSError *error;

NSArray *games = [context executeFetchRequest:fetchRequest error:&error];

if (games == nil) {
    NSLog(@"There was an error!");
}

int noOfBatOuts = games.count;
int noOfNotOuts=0;

for (NSManagedObject *oneMatch in games) {

     if ([oneMatch valueForKey:@"batOut"]==@"NO") {
            noOfBatOuts = noOfBatOuts - 1;
            noOfNotOuts = noOfNotOuts + 1;
            NSLog(@"Not Out!");
     }

     NSLog(@"How out %@",[oneMatch valueForKey:@"batOut"]);

}

notOuts.text=[NSString stringWithFormat:@"%d",(noOfNotOuts)];

NSLog(@"No of Not Outs is %@",notOuts.text);

When I run with data that has a not out string - NO, - the NSLog(@"Not Out!") is never called and the final NSLog(@"No of Not Outs...) reports zero. However I know that the data is there and it开发者_C百科 is identified in the middle NSLog(@"How Out....).

I am starting to tear my hair out in frustration and not having the knowledge yet to know the answer. Can anybody help please?

I would assume that batOut is a Boolean rather than string type, in which case you should be checking for truth rather than string equality.

If batOut really is a string, then you still can't compare strings this way. You need to use isEqual: or isEqualToString:. For example:

 if ([[oneMatch valueForKey:@"batOut"] isEqual:@"NO"]) {

Normally you'd use isEqualToString: for string comparisons, but -valueForKey: is an id so isEqual: is safer.

The == operator checks that two pointers have the same value. Two strings can have the same contents but not be stored in the same memory.

You can't compare strings with ==. Use NSString's isEqualToString: