dmhts

/**
 * Bulletproof singletone constructor. Can be used with or 
 * without new, can be called from whatever (object method,
 * standalone function). Works fine in strict mode
 */
var Singletone = (function () {
	var instance;

	return function Construct_singletone () {
		if (instance) {

dmhts

// - MARK: - Swift

let startTime = CACurrentMediaTime()
// Code to test
print("Runtime: \((CACurrentMediaTime() - startTime) * 1000) ms")

// MARK: - Obj-C

// Measuring runtime of the particular part of code
CFTimeInterval startTime = CACurrentMediaTime();

dmhts

+ (instancetype)sharedInstance {
    static id sharedInstance = nil;
    
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sharedInstance = [[self alloc] init];
    });
    
    return sharedInstance;
}

dmhts

// MARK: Delegate approach

import UIKit

protocol ExampleViewModelDelegate: class {
    func someEventDidOccur()
}

class ExampleViewModel {
    weak var delegate: ExampleViewModelDelegate?