A simple UIImageView subclass that adds functionality to handle progress.
Drag the ProgressImageView.swift file into your project.
Just drag a simple UIImageView into your Storyboard/XIB file and under the Identity Inspector replace its class by ProgressImageView. Once done that, you can set its custom properties through the Attributes Inspector, since ProgressImageView is IBInspectable/IBDesignable.
The key property to use is progress, which is a CGFloat value that goes from 0 to 1.
A typical case of use is, for example, modifying that value inside a progress callback closure of an image upload.