Eduardo Bocato bocato

A dump of the SwiftUI.framework binary for the iOS simulator (as of Xcode 12.0 beta 2) using the swift-reflection-dump tool.

Note: I used a Swift 5.3 compiler build from a few weeks ago that I had laying around. Because of ABI stability, I don't think the swift-reflection-dump version has to match the compiler version that was used to build the binary, but I'm not 100% sure.

Replacing the SceneDelegate When Running Unit Tests

Overview

I've been working through the exercises in the excellent iOS Unit Testing by Example book by Jon Reid, which I highly recommend. However, the book is in beta at the moment and there are some curveballs thrown by iOS 13 that aren't handled in the text yet. Specifically, when I hit the section about using a testing AppDelegate class I thought "This is very good. But what about the SceneDelegate?"

In Chapter 4 the recommendation is to remove the @UIApplicationMain decoration and make a manual top-level call to UIApplicationMain. To wit:

import UIKit

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	import Foundation
	import InterposeKit
	import OSLog

	/// Hack tow work around Assertion failure in -[NSTouchBarLayout setLeadingWidgetWidth:], NSTouchBarLayout.m:78
	/// This sometimes happens when macOS restores a window.
	/// This even runs if there is no OS-level touch bar.
	class MacOSWorkarounds {
	static let logger = Logger(category: "MacOSWorkarounds")

	import SwiftUI

	/// Module A

	/// An outer module, which knows how to build ViewB with all
	/// its dependecies will set this closure.
	public var viewBFactory: (() -> AnyView)?

	class ViewAModel: ObservableObject {
	@Published var isShowingB = false

	import UIKit

	class RootViewController: UIViewController {
	override func viewDidAppear(_ animated: Bool) {
	super.viewDidAppear(animated)

	let text = "Cute cat"
	let image = UIImage(named: "cat.jpg")!

	// Note: you can't wrap the text and image into a single "TextImage" object and selectively return both or one as UIActivityItemSource doesn't like holding arrays

	#if canImport(Combine)

	import Combine
	import CasePaths

	@available(iOS 13.0, macOS 10.15, tvOS 13.0, watchOS 6.0, *)
	public typealias Effect<Output> = AnyPublisher<Output, Never>

	@available(iOS 13.0, macOS 10.15, tvOS 13.0, watchOS 6.0, *)
	extension Effect {


	extension Publisher {
	func cancellable<Id: Hashable>(id: Id) -> AnyPublisher<Output, Failure> {
	return Deferred { () -> PassthroughSubject<Output, Failure> in
	cancellables[id]?.cancel()
	let subject = PassthroughSubject<Output, Failure>()
	cancellables[id] = self.subscribe(subject)
	return subject
	}
	.eraseToAnyPublisher()

	extension Publishers {
	private struct IndexedResult<T> {
	let index: Int
	let result: T
	}

	private struct IndexedPublisher<Upstream>: Publisher where Upstream: Publisher {
	typealias Output = IndexedResult<Upstream.Output>
	typealias Failure = Upstream.Failure

	/*:
	This is a concept re-implementation of the @Binding and @State property wrappers from SwiftUI

	The only purpose of this code is to implement those wrappers myself
	just to understand how they work internally and why they are needed,

	⚠️ This is not supposed to be a reference implementation nor cover all
	subtleties of the real Binding and State types.
	The only purpose of this playground is to show how re-implementing
	them myself has helped me understand the whole thing better