Question

I have a problem I cannot solve with a Core Data entity.

In my entity there are two relations (whoHasToPay, whoHasToBePaid) and an attribute (howMuch).

This is the code in which I insert the record in the database

Debitcredit *dc = [NSEntityDescription
  insertNewObjectForEntityForName:@"Debitcredit"
  inManagedObjectContext:self.context];
dc.howMuch = [NSNumber numberWithFloat:5.2f];
dc.whoHasToPay = theDebitor;
dc.whoHasToBePaid = theCreditor;
NSLog(@"%@", dc);
[self.context save:&error];

The NSLog shows

<Debitcredit: 0x151590> (entity: Debitcredit; id: 0x141570 
  <x-coredata:///Debitcredit/t8DC4691F-5DE3-42D5-8095-C2D5D3264C8D2> ; data: {
  howMuch = "5.2";
  whoHasToBePaid = "0x140c50 <x-coredata://C25DC4FE-B46B-402C-B513-A2A83C6A9F86/Users/p1>";
  whoHasToPay = "0x14c280 <x-coredata://C25DC4FE-B46B-402C-B513-A2A83C6A9F86/Users/p2>";
})

so the value howMuch seems to be correct.

However, when I call it again with

fetchRequestCount = [[NSFetchRequest alloc] init];
entityCount = [NSEntityDescription entityForName:@"Debitcredit"      
  inManagedObjectContext:self.context];
[fetchRequestCount setEntity:entityCount];
fetchedObjectsCount = [self.context executeFetchRequest:fetchRequestCount error:&error];
for (Debitcredit *dc in fetchedObjectsCount) {
    NSLog(@"%f", [dc valueForKey:@"howMuch"]);
    NSLog(@"%@", [[dc valueForKey:@"whoHasToPay"] name]);
    NSLog(@"%@", [[dc valueForKey:@"whoHasToBePaid"] name]);
}
[fetchRequestCount release];

the NSLog shows

2010-12-05 01:47:04.636 myApp[6179:307] 0.000000
2010-12-05 01:47:04.642 myApp[6179:307] John
2010-12-05 01:47:04.646 myApp[6179:307] Jack

It seems that howMuch has become zero. Why? Am I wrong?

Answer 1

It is a logging error. Floats and other numerical values are stored as NSNumber objects. This:

[dc valueForKey:@"howMuch"]

… returns an NSNumber object and not a float value. You need to change the log to:

NSLog(@"%@", [dc valueForKey:@"howMuch"]);

… and you should see the correct value.