main.m

#import <Foundation/Foundation.h>

@interface Foo : NSObject
@end

@interface Bar : NSObject
@end

@implementation Foo
@end

@implementation Bar
@end

int main (int argc, const char * argv[])
{
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
	
	NSMutableArray *array = [NSMutableArray arrayWithObjects:[Foo new], [Foo new], [Bar new], [Foo new], [Bar new], [Bar new], nil];
	NSPredicate *p = [NSPredicate predicateWithFormat:@"self.class == %@", [Foo class]];
	NSLog(@"%@\n%@", array, [array filteredArrayUsingPredicate:p]);

    [pool drain];
    return 0;
}