Question

Is there a way construct a predicate to filter by class type?

I currently loop through the array and check to the class of each object. Maybe there is a cleaner way?

Answer 1

You could add a category to NSObject that adds a “cf_className” method, like so:

@interface NSObject (CFAdditions)
- (NSString *) cf_className;
@end

@implementation NSObject (CFAdditions)
- (NSString *) cf_className {
  return NSStringFromClass([self class]);
}
@end

From there, you can use predicates like:

NSPredicate * p = [NSPredicate predicateWithFormat:@"cf_className = %@", aClass];
NSArray * filtered = [anArray filteredArrayUsingPredicate:p];

If you’re on the Mac, you can just use -[NSObject className] instead of having to create the category. The iPhone doesn’t have that method, hence the need for a category.