Form NSPredicate from string that contains id's

Question

I have this problem where I can\'t think of how to write this predicate.

I have an Entity called Contact, it has a string property \"pages\", let\'s say

Answer 1

The "MATCHES" operator of NSPredicate can be used to compare against a regular expression:

NSString *pageId = @"1";
NSString *regex = [NSString stringWithFormat:@"(.*,)?%@(,.*)?", pageId];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"pages MATCHES %@", regex];

But you should also consider to replace the string property by a to-many relationship to a Page entity, then the predicate would look like

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"ANY pages.pageid == %@", pageId];