TerryCK

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        
        window = UIWindow(frame: UIScreen.main.bounds)
        window?.makeKeyAndVisible()
        window?.rootViewController = UINavigationController(rootViewController: ViewController())
        
        return true
    }

TerryCK

import UIKit

class ViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        title = "ViewController"
        view.backgroundColor = UIColor.brown
    }
    

TerryCK

class HTMLElement {
    let name: String
    let text: String
    
    // 參考self的closure造成 記憶體無法釋放的retain cycle
    lazy var asHTML: () -> String = {
        return "<\(self.name)>\(self.text)</\(self.name)>"
    }

    init(name: String, text: String) {

TerryCK

class HTMLElement {
    let name: String
    let text: String
    
    
    lazy var asHTML: () -> String = {
        [weak self] in  //以弱參考修飾捕獲的self使參考計數不計
        return "<\(self?.name)>\(self?.text)</\(self?.name)>"，// 因為weak是弱參考屬optional所以在鏈上需要加入?使用
    }

TerryCK

    lazy var asHTML: () -> String = {
        [weak self] in
        guard let this = self else { return "" }
        return "<\(this.name)>\(this.text)</\(this.name)>"
    }
    //換個角度來看self，先用guard let 安全的解包 optional self，在來使用this

TerryCK

import Foundation


// Two object retain cycle pattern
class Person: NSObject {
    var name: String
    var deparment: Department?
    init(name:String) {
        self.name = name
    }

TerryCK

let redView = UIView()
    redView.backgroundColor = .red
    
    view.addSubview(redView)
    redView.translatesAutoresizingMaskIntoConstraints = false
    
    redView.topAnchor.constraint(equalTo: view.topAnchor, constant: 40).isActive = true
    redView.rightAnchor.constraint(equalTo: view.rightAnchor, constant: -40).isActive = true
    redView.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 40).isActive = true
    redView.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -100).isActive = true

TerryCK

    let redView = UIView()
    redView.backgroundColor = .red
    view.addSubview(redView)
    redView.translatesAutoresizingMaskIntoConstraints = false
    
    NSLayoutConstraint.activate([
    redView.topAnchor.constraint(equalTo: view.topAnchor, constant: 40),
    redView.rightAnchor.constraint(equalTo: view.rightAnchor, constant: -40),
    redView.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 40),
    redView.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -100),

TerryCK

class SingletonClass {
    static let shared = SingletonClass() 
    private init() { }
    func someMethod() { }
    let constantProperty = ""
    var variableProperty = ""
}

TerryCK

SingletonClass.shared.constantProperty
SingletonClass.shared.someMethod()
SingletonClass.shared.variableProperty