A simple throttler helper class written in Swift 4.0.
A full blog post on this topic can be found here: Simple Throttling in Swift. ###Example
class Throttler {
private var workItem: DispatchWorkItem = DispatchWorkItem(block: {})
private var previousRun: Date = Date.distantPast
private let queue: DispatchQueue
private let minimumDelay: TimeInterval
init(minimumDelay: TimeInterval, queue: DispatchQueue = DispatchQueue.main) {
self.minimumDelay = minimumDelay
self.queue = queue
}
func throttle(_ block: @escaping () -> Void) {
// Cancel any existing work item if it has not yet executed
workItem.cancel()
// Re-assign workItem with the new block task, resetting the previousRun time when it executes
workItem = DispatchWorkItem() {
[weak self] in
self?.previousRun = Date()
block()
}
// If the time since the previous run is more than the required minimum delay
// => execute the workItem immediately
// else
// => delay the workItem execution by the minimum delay time
let delay = previousRun.timeIntervalSinceNow > minimumDelay ? 0 : minimumDelay
queue.asyncAfter(deadline: .now() + Double(delay), execute: workItem)
}
}###Use case
let throttler = Throttler(minimumDelay: 0.5)
func frequentlyCalledMethod() {
// Throttling our computationally expensive task will ensure
// that it is only run once after 0.5 seconds have elapsed since last being requested,
// preventing excessive computation in the case that this method is called with high frequency
throttler.throttle {
computationallyExpensiveTask()
}
}
func computationallyExpensiveTask() {
// It's a fake! 😱
}