NativeScript/packages/core/timer/index.ios.ts

//iOS specific timer functions implementation.
const timeoutCallbacks = new Map<number, KeyValuePair<NSTimer, TimerTargetImpl>>();
let timerId = 0;

interface KeyValuePair<K, V> {
	k: K;
	v: V;
}

@NativeClass
class TimerTargetImpl extends NSObject {
	private callback: Function;
	private disposed: boolean;
	private id: number;
	private shouldRepeat: boolean;

	public static initWithCallback(callback: Function, id: number, shouldRepeat: boolean): TimerTargetImpl {
		const handler = <TimerTargetImpl>TimerTargetImpl.new();
		handler.callback = callback;
		handler.id = id;
		handler.shouldRepeat = shouldRepeat;

		return handler;
	}

	public tick(timer): void {
		if (!this.disposed) {
			this.callback();
		}

		if (!this.shouldRepeat) {
			this.unregister();
		}
	}

	public unregister() {
		if (!this.disposed) {
			this.disposed = true;

			const timer = timeoutCallbacks.get(this.id).k;
			timer.invalidate();
			timeoutCallbacks.delete(this.id);
		}
	}

	public static ObjCExposedMethods = {
		tick: { returns: interop.types.void, params: [NSTimer] },
	};
}

function createTimerAndGetId(callback: Function, milliseconds: number, shouldRepeat: boolean): number {
	// Cast to Number
	milliseconds += 0;

	timerId++;
	const id = timerId;
	const timerTarget = TimerTargetImpl.initWithCallback(callback, id, shouldRepeat);
	const timer = NSTimer.scheduledTimerWithTimeIntervalTargetSelectorUserInfoRepeats(milliseconds / 1000, timerTarget, 'tick', null, shouldRepeat);

	// https://github.com/NativeScript/NativeScript/issues/2116
	NSRunLoop.currentRunLoop.addTimerForMode(timer, NSRunLoopCommonModes);

	const pair: KeyValuePair<NSTimer, TimerTargetImpl> = {
		k: timer,
		v: timerTarget,
	};
	timeoutCallbacks.set(id, pair);

	return id;
}

export function setTimeout(callback: Function, milliseconds = 0, ...args): number {
	const invoke = () => callback(...args);

	return createTimerAndGetId(zonedCallback(invoke), milliseconds, false);
}

export function clearTimeout(id: number): void {
	const pair = timeoutCallbacks.get(<number>(<any>id));
	if (pair && pair.v) {
		pair.v.unregister();
	}
}

export function setInterval(callback: Function, milliseconds = 0, ...args): number {
	const invoke = () => callback(...args);

	return createTimerAndGetId(zonedCallback(invoke), milliseconds, true);
}

export const clearInterval = clearTimeout;