UITask.swift

import UIKit
import Combine

public extension Task {
	/// Keep a reference to a task that can be cancelled.
	func store(in set: inout Set<AnyCancellable>) {
		set.insert(AnyCancellable {
			self.cancel()
		})
	}
}

// Options A: automatically attach tasks to an object using associated objects
// on deinit AnyCancellable will be released and cancel the task

private let tasksKey = UnsafeRawPointer(UnsafeMutablePointer<UInt8>.allocate(capacity: 1))
public extension NSObject {
	func task(priority: TaskPriority = .userInitiated, _ action: @escaping @Sendable () async -> Void) {
		let task = Task(priority: priority, operation: action)
		
		var tasks = objc_getAssociatedObject(self, tasksKey) as? Set<AnyCancellable> ?? []
		task.store(in: &tasks)
		objc_setAssociatedObject(self, tasksKey, tasks, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
	}
}

class AViewController: UIViewController {
	override func viewDidLoad() {
		super.viewDidLoad()
		
		task {
			try? await Task.sleep(nanoseconds: 1_000_000_000)
		}
	}
}

// Option B: more explicitly store the tasks

class BViewController: UIViewController {
	private var observers: Set<AnyCancellable> = []
	
	override func viewDidLoad() {
		super.viewDidLoad()
		
		Task {
			try await Task.sleep(nanoseconds: 1_000_000_000)
		}
		.store(in: &observers)
	}
}

// Option C: don't worry about it

class CViewController: UIViewController {
	override func viewDidLoad() {
		super.viewDidLoad()
		
		// task will never be cancelled, but maybe that's fine
		Task {
			try await Task.sleep(nanoseconds: 1_000_000_000)
		}
	}
}