UIViewPreviewProvider

This is a helper class for displaying UIViews inside the Xcode preview canvas meant to display SwiftUI.
It allows you to quickly iterate on your UIViews without having to rebuild your entire app.
This is especially useful if your project needs to supports iOS < 13 and you can't start using SwiftUI just yet.

Adding UIViewPreviewProvider to your project.

Just copy UIViewPreviewProvider.swift into your project. I don't think this is large enough to warrant adding a whole library to your project.

Rendering UIView previews in your project

In the file where your view is defined:

// This if check is important if you're working with a project that supports iOS < 13
// If you're working with an iOS 13+ project then you can omit the canImport(SwiftUI) check
#if canImport(SwiftUI) && DEBUG

import SwiftUI

@available(iOS 13.0, *)
struct MyView_Preview: PreviewProvider, UIViewPreviewProvider {
    
    // Provide previews of your UIView
    static let uiPreviews: [Preview] = {

        // Create your views and populate them with some dummy data
        
        let view1 = MyView()
        view1.someProperty = "foo"
        let view1Preview = Preview(view1, displayName: "View 1")

        let view2 = MyView()
        view2.someProperty = "bar"
        let view2Preview = Preview(view2, displayName: "View 2")

        return [view1Preview, view2Preview]
    }()
}

#endif

Open up the preview Xcode canvas by pressing (⌥ + ⌘ + return) and your previews should show up.

You may need to hit the Resume button for them to show up

It should look something like this:

Examples

See Example.swift for more info.

If you're using MVVM see MVVM Example.swift to see how you can generate previews directly from your ViewModels.