Use case: To prevent button from being tapped multiple times

Throttle.swift

extension DispatchQueue {
  func throttle(delay: DispatchTimeInterval) -> (_ block: @escaping () -> Void) -> Void {
    var lastFireTime: DispatchTime = .now()

    return { [weak self, delay] block in
      let deadline: DispatchTime = .now() + delay
      
      self?.asyncAfter(deadline: deadline) { [delay] in
          let now: DispatchTime = .now()
          let when: DispatchTime = lastFireTime + delay
          if now < when { return }
          lastFireTime = .now()
          block()
      }
    }
  }
}