NSObject category with method to get class of a property

gistfile1.m

@interface NSObject (classNameOfPropetyName)
- (Class)classOfPropetyName:(NSString *)propertyName;
@end
@implementation NSObject (classNameOfPropetyName)
- (Class)classOfPropetyName:(NSString *)propertyName {
    static NSRegularExpression *re = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        // T@"NSString",&,N,Vtest
        re = [[NSRegularExpression alloc] initWithPattern:@"@\"([^\"]*)\""
                                                  options:0
                                                    error:NULL];
    });
    
    objc_property_t prop = class_getProperty([self class], [propertyName UTF8String]);
    if (prop == NULL) {
        return nil;
    }
    
    NSString *attrs = [NSString stringWithUTF8String:property_getAttributes(prop)];
    NSArray *matches = [re matchesInString:attrs options:0 range:NSMakeRange(0, [attrs length])];
    if ([matches count] == 0) {
        return nil;
    }
    
    NSTextCheckingResult *result = [matches objectAtIndex:0];
    if ([result rangeAtIndex:1].location == NSNotFound) {
        return nil;
    }
    
    return NSClassFromString([attrs substringWithRange:[result rangeAtIndex:1]]);
}
@end