새로 알아간 것들

sfSymbol

reference

Optional

조건은 옵셔널과 텍스트 비교할 때는 Unrapping안해도 비교 가능

reference

usleep

usleep(1000000) //will sleep for 1 second

UIView.animate

크기가 늘어났다 줄어드는 animation

UIView.animate(withDuration: 0.2)  {
    self.txtTime.transform = CGAffineTransform.init(scaleX: 2.0, y: 2.0)
} completion: { (_) in
    UIView.animate(withDuration: 0.4) {
        self.txtTime.transform = CGAffineTransform.identity
    }
}