vialyx

lazy var loginCompletion: (Bool) -> Void = { [weak self] success in
    if let `self` = self, success {
        self.navigationController?.popToRootViewController(animated: true)
    }
}
/*
 [weak self] is closure capture list. It can be added all parameters what you need.
 i.e. [weak self, unowned delegate]
 */

vialyx

// MARK: - Strong reference cycle for closures
class ViewController: UIViewController {
    
    lazy var loginCompletion: (Bool) -> Void = { success in // <- place where we has been mistaken. It must be resolved using capture list with 'unowned' reference
        if success {
            self.navigationController?.popToRootViewController(animated: true)
        }
    }
    
    deinit {

vialyx

// MARK: - Strong reference cycle
class Owner {
    
    let udid: String
    let iin: String
    let name: String
    var business: Business!
    
    init(udid: String, iin: String, name: String) {
        self.udid = udid

vialyx

// MARK: - unowned reference. Prevent strong reference cycle
class Owner {
    
    let udid: String
    let iin: String
    let name: String
    var business: Business!
    
    init(udid: String, iin: String, name: String) {
        self.udid = udid

vialyx

// MARK: - weak reference
weak var weakCustomer1stRef: Customer? = nil
weak var weakCustomer2stRef: Customer? = nil

weakCustomer1stRef = Customer(udid: "weak 1", name: "Jacob")
/*
 print: weak 1 initialized
 print: weak 1 deinitialized
 */

vialyx

// MARK: - strong reference counting
var customer1stRef: Customer? = nil
var customer2ndRef: Customer? = nil

customer1stRef = Customer(udid: "1st", name: "Maxim")
/*
 print: 1st initialized
 */
customer2ndRef = customer1stRef
customer1stRef = nil

vialyx

//: Playground - noun: a place where people can play

import UIKit

class Customer {
    
    let udid: String
    let name: String
    
    init(udid: String, name: String) {

vialyx

// MARK: API availability

var color: UIColor?

if #available(iOS 11, *) {
    // Use iOS 11 APIs on iOS
    color = UIColor(named: "green_color_from_asset_folder")
} else {
    // Fall back to earlier iOS APIs
    color = UIColor.green

vialyx

// MARK: guard

typealias JSON = [String: Any?]

struct Account {
    let udid: String
    let token: String
}

extension Account {

vialyx

// MARK: Continue, break, throw

let numbers: [Int] = [1, 2, 3, 4, 5, 10, 11, 20]

// MARK: continue
var evenSum = 0
for number in numbers {
    if number % 2 != 0 { continue }
    
    evenSum += number