Generic asynchronous images in SwiftUI

AsyncImage.swift

protocol ImageLoader {
    var image: UIImage? { get }
    func fetchImage(forSize size: CGSize)
    func cancelFetch()
}

struct AsyncImage<Loader: ObservableObject & ImageLoader>: View {
    
    @ObservedObject var loader: Loader
    
    var body: some View {
        GeometryReader { reader in
            Group {
                if self.loader.image != nil {
                    Image(uiImage: self.loader.image!)
                        .resizable()
                        .scaledToFill()
                        .position(x: reader.size.width / 2, y: reader.size.height / 2)
                        .clipped()
                } else {
                    Text("THERE'S NO FUCKEN IMAGE")
                }
            }
            .onAppear { self.loader.fetchImage(forSize: reader.size) }
            .onDisappear { self.loader.cancelFetch() }
        }
    }
    
}