Debounce vs Throttle: what's the difference, and implement throttle

Middle PRO

Task

You're given a debouncer. Explain how debounce differs from throttle, find the weak spots in the code, and write a Throttler.

final class Debouncer {
    private let delay: TimeInterval
    private let queue: DispatchQueue
    private var workItem: DispatchWorkItem?

    init(delay: TimeInterval, queue: DispatchQueue = .main) {
        self.delay = delay
        self.queue = queue
    }

    func run(_ action: @escaping () -> Void) {
        workItem?.cancel()
        let item = DispatchWorkItem(block: action)
        workItem = item
        queue.asyncAfter(deadline: .now() + delay, execute: item)
    }
}