Hell of Shovelers - shovelers.net

끝까지위로 뒤집는 컬 효과는 UIViewAnimationTransitionCurlUp
또는 UIModalTransitionStylePartialCurl 등으로 효과를 낼 수 있다. 
하지만 원하는것은 절반만 뒤집어 아래에 숨겨진 버튼을 사용하는것.
구글에게 물었더니 다음과같이 따끈따근한 예제가!
 
CATransition *animation = [CATransition animation];

[animation setDelegate:self];

[animation setDuration:0.35];

[animation setTimingFunction:UIViewAnimationCurveEaseInOut];

if (!curled){

animation.type = @"pageCurl";

animation.fillMode = kCAFillModeForwards;

animation.endProgress = 0.58;

    } else {

animation.type = @"pageUnCurl";

        animation.fillMode = kCAFillModeBackwards;

animation.startProgress = 0.42;

}

[animation setRemovedOnCompletion:NO];

[[logo.view layer] addAnimation:animation forKey:@"pageCurlAnimation"];

if (!curled) {

logo.view.alpha = 0;

} else {

logo.view.alpha = 1;

}

curled = !curled;