How to download images async for WidgetKit

Question

I am developing Widgets for iOS and I really don't know how to download images for the widgets.

The widget currently downloads an array of Objects, and every object has a URL of an image. The idea is that every object makes a SimpleEntry for the Timeline.

What's the best way of achieving this? I read that Widgets shouldn't use the ObservableObject. I fetch the set of objects in the timeline provider, which seems to be what Apple recommends. But do I also download the images there and I wait until all are done to send the timeline?

Any advice would be very helpful,

Answer 1

Yes, you should download the images in the timeline provider and send the timeline when they are all done. Refer to the following recommendation by an Apple frameworks engineer.

I use a dispatch group to achieve this. Something like:

let imageRequestGroup = DispatchGroup()
var images: [UIImage] = []
for imageUrl in imageUrls {
    imageRequestGroup.enter()
    yourAsyncUIImageProvider.getImage(fromUrl: imageUrl) { image in
        images.append(image)
        imageRequestGroup.leave()
    }
}
imageRequestGroup.notify(queue: .main) {
    completion(images)
}

I then use SwiftUI's Image(uiImage:) initializer to display the images