用block实现两个页面间的传值

@property (nonatomic, copy) void(^doTransferMsg)(NSString *_msg);

- (IBAction)transferText:(UIButton *)sender {
  if (_doTransferMsg) {
    _doTransferMsg(@"hello there");
    _doTransferMsg = nil;
  }
  [self.navigationController popViewControllerAnimated:YES];
}

- (IBAction)LoadDetailView:(UIButton *)sender {
  [ibTextLabel setText:nil];
  DetailViewController *_curDetail = [[DetailViewController alloc] initWithNibName:@"DetailViewController"
                                                                            bundle:nil];
  [_curDetail setDoTransferMsg:^(NSString *_msg) {
    dispatch_async(dispatch_get_main_queue(), ^{
      [ibTextLabel setText:_msg];
    });
  }];
  [self.navigationController pushViewController:_curDetail
                                       animated:YES];
  [_curDetail release];
}