Question

I have a simple predicate driving me crazy.

NSString *name;
NSDate *myDate;

-(void)fetch:(NSString *)name Date:(NSDate *)myDate
{
  ...
  //predicate
  NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name = %@ AND myDate = %@",name,myDate];
  [req setPredicate:predicate];
}

-(void)fetch2:(NSString *)predicateStr
{
   ...
  //predicate
  NSPredicate *predicate = [NSPredicate predicateWithFormat:predicateStr];
  [req setPredicate:predicate];
}

////// call #1/////
[self fetch:name Date:myDate]; //WORKS

////// call #2/////
NSString *predicateStr = [NSString stringWithFormat:@"name = %@ AND myDate = %@",name,myDate];
[self fetch2:predicateStr]; 

//Call#2 doesn’t work – Can’t parse Date ?? Aren’t they identical? The parameters are the same, no change in values. Note, the Date parameter is the problem, the NSString parameter works fine without the Date.

Answer 1

No, they’re not the same.

For Call #1, here’s what you’re passing in to +predicateWithFormat::

@"name = %@ AND myDate = %@"

For Call #2, here’s what you’re passing in to +predicateWithFormat::

@"name = Some Name AND myDate = 2012-10-17 8:05:42 PM -0800"

The first one is a valid predicate format string, and thus it works. The second is not a valid predicate format string, and thus it fails.