SwiftUI modifier to show a view only a given amount of app runs.

ShowForAppRuns.swift

// Depends on https://github.com/sindresorhus/Defaults
@available(macOS 10.15, *)
private struct ShowForAppRuns: ViewModifier {
	private static var runCounts = [String: Int]()

	private let count: Int
	private let startShowingFromAppRun: Int
	private let runCount: Int

	init(count: Int, id: String, startShowingFromAppRun: Int = 1) {
		assert(startShowingFromAppRun >= 1)
		self.count = count
		self.startShowingFromAppRun = startShowingFromAppRun

		self.runCount = {
			guard let count = Self.runCounts[id] else {
				let key = Defaults.Key<Int>("SS_ShowForAppRuns_\(id)", default: 0)
				Defaults[key] += 1
				let count = Defaults[key]
				Self.runCounts[id] = count
				return count
			}

			return count
		}()
	}

	func body(content: Content) -> some View {
		if
			runCount >= startShowingFromAppRun,
			runCount < (count + startShowingFromAppRun)
		{
			return AnyView(content)
		} else {
			return AnyView(EmptyView())
		}
	}
}

@available(macOS 10.15, *)
extension View {
	// TODO: Improve method and parameter naming.
	/**
	Show the view only for the given amount of app runs.

	- Parameter count: Show the view this many app runs.
	- Parameter id: Identifier for the view. Should be unique in the app. Prefer camel case notation.
	- Parameter startShowingFromAppRun: Start showing the view at this app run count.

	Tip: Specify `0` as `count` to see how it will look like as hidden.

	```
	// This shows the text on the second time the app is run and shows it for two app runs.
	Text("🦄").showForAppRun(2, id: "unicornText", startShowingFromAppRun: 2)
	```
	*/
	func showForAppRuns(_ count: Int, id: String, startShowingFromAppRun: Int = 1) -> some View {
		modifier(ShowForAppRuns(count: count, id: id, startShowingFromAppRun: startShowingFromAppRun))
	}
}