UISearchBar.m

@implementation UISearchBar (RAC)
- (RACSignal *)rac_editing {
  // Pretend we have an ivar I know we'd use setAssociatedObject
  _proxy = [[RACDelegateProxy alloc] initWithProtocol: @protocol(UISearchBarDelegate)];
  return [@[
    [[_proxy signalForSelector: @selector(searchBarTextDidBeginEditing:)] mapReplace: @YES],
    [[_proxy signalForSelector: @selector(searchBarTextDidEndEditing:)] mapReplace: @NO]
  ].rac_sequence.signal switchToLatest];
}
@end