Scheduled task wrapper

Scheduled.swift

import Foundation

extension Bundle {
    var id: String { bundleIdentifier ?? "" }
}

@propertyWrapper
public class Scheduled {
    private static let defaultQueue = DispatchQueue(
        label: Bundle.main.id.appending(".queues.scheduled"),
        qos: .utility,
        autoreleaseFrequency: .workItem
    )
    
    private let lock = NSLock()
    private(set) var isSuspended = false
    
    public let interval: TimeInterval
    public let delay: TimeInterval
    public let queue: DispatchQueue
    public var action: () -> Void
    
    public init(
        interval: TimeInterval,
        delay: TimeInterval = 0,
        action wrappedValue: @escaping () -> Void = {})
    {
        self.interval = interval
        self.delay = delay
        self.queue = Scheduled.defaultQueue
        self.action = wrappedValue
    }
    
    public init(
        interval: TimeInterval,
        delay: TimeInterval = 0,
        queue: DispatchQueue,
        action wrappedValue: @escaping () -> Void = {})
    {
        self.interval = interval
        self.delay = delay
        self.queue = queue
        self.action = wrappedValue
    }
    
    public var wrappedValue: () -> Void {
        get { action }
        set {
            action = newValue
            resume()
        }
    }
    
    public func suspend() {
        lock.store(true, in: &isSuspended)
    }
    
    public func resume() {
        lock.store(false, in: &isSuspended)
        queue.asyncAfter(deadline: .now() + delay) {
            self.runLoop()
        }
    }
    
    private func runLoop(_ active: Bool = true) {
        guard active else { return }
        action()
        
        let shouldStopExecution = isSuspended
        queue.asyncAfter(deadline: .now() + interval) { [weak self] in
            self?.runLoop(!shouldStopExecution)
        }
    }
    
}

UsageExample

class CounterViewController: UIViewController {
    @Scheduled(interval: 1) 
    private var updateLabel: () -> Void

    private var count: Int = 0

    override func loadView() { self.view = UILabel() }

    override func viewDidLoad() {
        super.viewDIdLoad()
        updateLabel = { [weak self]
            self?.count += 1
            self?.label.text = String(self?.count ?? 0)
        } // starts automatically
    }
}

Also you can use

_updateLabel.suspend() // pauses execution
_updateLabel.resume() // continues execution
_updateLabel.isSuspended

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