Throttler

Throttler.swift

import Foundation
​
public class Throttler {
    private var workItem = DispatchWorkItem(block: {})
    private var previousRun = Date.distantPast
    
    private let queue: DispatchQueue
    private let minimumDelay: TimeInterval
​
    public init(minimumDelay: TimeInterval, queue: DispatchQueue = DispatchQueue.main) {
        self.minimumDelay = minimumDelay
        self.queue = queue
    }
​
    public func throttle(_ block: @escaping () -> Void) {
        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)
    }
    
    public func cancel() {
        // Cancel any existing work item if it has not yet executed
        workItem.cancel()
    }
    
}

// Usage

private var throttler = Throttler(minimumDelay: 0.50)

navigation?.searchTextfield.onTextDidChange = { [weak self] text in
            guard let self = self else { return }
            self.throttler.throttle {
                guard let text = text, text.count > 1 else {
                    self.reloadTable()
                    self.searching = false
                    return
                }
                if !self.searching {
                    self.reloadTable(loading: true)
                    self.searching = true
                }
                if let lat = self.currentLocation?.latitude, let lon = self.currentLocation?.longitude {
                    self.reloadTable(text: text, proximity: "\(String(lat)),\(String(lon))")
                } else {
                    self.reloadTable(text: text, proximity: self.viewModel.suggestProximity())
                }
            }
        }