Have to setting for UICloudSharingController.

Preset for use UICloudSharingController.

About convert from BASE64URL to BASE64.

BASE64URL -> BASE64.

Zooming image with UIScrollView.

Zooming image by viewForZooming in UIScrollViewDelegate.

Tracking keyboard frame changed.

Tracking keyboard frame using Key value observing.

Fast paging flowlayout for UICollectionView.

Source for FastPagingFlowLayout.

Precondition for multitasking app.

Several step to your app for multitasking.