Throttler.swift

import Foundation

public class Throttler<T> {
    private(set) var value: T? = nil
    private var valueTimestamp: Date? = nil
    private var interval: TimeInterval
    private var queue: DispatchQueue
    private var callbacks: [(T) -> ()] = []
    public init(_ interval: TimeInterval, on queue: DispatchQueue = .main) {
        self.interval = interval
        self.queue = queue
    }
    public func receive(_ value: T) {
        self.value = value
        guard valueTimestamp == nil else { return }
        self.valueTimestamp = Date()
        queue.asyncAfter(deadline: .now() + interval) { [weak self] in
            self?.onDispatch()
        }
    }
    public func on(throttled: @escaping (T) -> ()) {
        self.callbacks.append(throttled)
    }
    private func onDispatch() {
        self.valueTimestamp = nil
        sendValue()
    }
    private func sendValue() {
        if let value = self.value { callbacks.forEach { $0(value) } }
    }
}