static auto disappearingPreviousComponentAnimation()

in ComponentKit/Components/CKTransitionComponent.mm [27:73]
44 lines of code
3 McCabe index (conditional complexity)

static auto disappearingPreviousComponentAnimation(CAAnimation *disappearAnimation,
                                                   CKComponent *previousComponent,
                                                   CKComponent *newComponent) -> CKComponentAnimation
{
  return CKComponentAnimationHooks{
    .willRemount = ^{
      auto const childView = [previousComponent viewForAnimation];
      RCCAssertWithCategory(
                            childView != nil,
                            [previousComponent className],
                            @"Can't animate component without a view. "
                            "Check %@ is from the previousComponent tree, has a view and is mounted.",
                            [previousComponent className]
                            );

      auto const snapshotView = [childView snapshotViewAfterScreenUpdates:NO];
      snapshotView.layer.anchorPoint = childView.layer.anchorPoint;
      snapshotView.userInteractionEnabled = NO;
      return snapshotView;
    },
    .didRemount = ^UIView *(UIView *snapshotView) {
      auto const newView = [newComponent viewForAnimation];
      RCCAssertWithCategory(newView != nil, [newComponent className], @"Can't animate %@ without a view.", [newComponent className]);
      if (newView == nil || snapshotView == nil) {
        return nil; // Avoid crashing in insertSubview:aboveSubview:
      }
      auto const frame = CGRect{
        newView.frame.origin,
        snapshotView.bounds.size,
      };
      snapshotView.frame = frame;
      [newView.superview insertSubview:snapshotView aboveSubview:newView];

      [CATransaction begin];
      [CATransaction setCompletionBlock:^{
        [snapshotView removeFromSuperview];
      }];
      [snapshotView.layer addAnimation:disappearAnimation forKey:nil];
      [CATransaction commit];

      return snapshotView;
    },
    .cleanup = ^(UIView *snapshotView) {
      [snapshotView removeFromSuperview];
    },
  };
}