Question

I’m trying to create a predicate to sort an array of objects that have a date property. However, when I try to NSLog the predicate, an exception is raised and I get a strange error.

Here’s the code:

NSDateFormatter * dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"yyyy"];
NSDate * minDate = [dateFormatter dateFromString:@"2011"];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"date >= %@ ", minDate];
NSLog(predicate);

Here’s the error:

2012-02-04 12:45:58.400 MyApp[42746:17303] -[NSComparisonPredicate length]: unrecognized selector sent to instance 0x9359000

So, why is this happening and how can I fix it?

Answer 1

try: NSLog(@"%@", predicate)

NSLog expects a NSString, that works as an format string. The number of format specifiers in the format string will specify, how many arguments need to follow.

from the doc:

NSLog
Logs an error message to the Apple System Log facility.

void NSLog (
   NSString *format,
   ...
);  

Discussion
Simply calls NSLogv, passing it a variable number of
arguments.