ahmedk92

import UIKit

class ViewController: UIViewController {
    
    private lazy var button: UIButton = {
        let button = UIButton(frame: .zero)
        button.setTitle("Hi", for: .normal)
        button.backgroundColor = .red
        button.setTitleColor(.white, for: .normal)
        return button

ahmedk92

extension WKWebView {
    enum EvaluateJavaScriptError: String, Error {
        case typeMismatchError
    }
    func evaluateJavaScript(_ javaScriptString: String, completionHandler: ((Result<String, Error>) -> Void)? = nil) {
        evaluateJavaScript(javaScriptString) { (result, error) in
            guard let result = result else {
                completionHandler?(.failure(error!))
                return
            }

ahmedk92

extension UIView {
    func traverse<T>(visitor: (T) -> ()) {
        for subview in subviews {
            if let tView = subview as? T {
                visitor(tView)
            }
            
            subview.traverse(visitor: visitor)
        }
    }

ahmedk92

class PageViewController: UIPageViewController {
    override func setViewControllers(_ viewControllers: [UIViewController]?, direction: UIPageViewController.NavigationDirection, animated: Bool, completion: ((Bool) -> Void)? = nil) {
        super.setViewControllers(viewControllers, direction: direction, animated: animated) { (isFinished) in
            if  isFinished && animated {
                DispatchQueue.main.async {
                    super.setViewControllers(viewControllers, direction: direction, animated: false, completion: nil)
                }
            }
            
            completion?(isFinished)

ahmedk92

- (void)commonInit {
    // Do stuff.
}

- (instancetype)init {
    if (self = [super init]) {
        [self commonInit];
    }
    
    return self;

ahmedk92

let range = 0..<5000

// Hogs up to GBs of memory till total evaluation.
let items: [Item] = Array(range).map({ Item(id: $0) })

// Frees memory soon after every evaluation.
let items: [Item] = Array(range).autoreleasingMap({ Item(id: $0) })

ahmedk92

infix operator &&&: LogicalConjunctionPrecedence
extension Bool {
    static func &&& (left: Bool, right: Bool) -> Bool {
        return left && right
    }
}

ahmedk92

// =====================================
// NO RETAIN CYCLE

class ViewController: UIViewController {
    private var dataSource = DataSource() // Strong reference. But in just one way; no cycle.
}

class DataSource: NSObject, UITableViewDataSource {

}

ahmedk92

class MyApplication: UIApplication {
    override init() {
        let notFirstOpenKey = "notFirstOpen"
        let notFirstOpen = UserDefaults.standard.bool(forKey: notFirstOpenKey)
        if notFirstOpen == false {
            UserDefaults.standard.set(["ar"], forKey: "AppleLanguages")
            UserDefaults.standard.set(true, forKey: notFirstOpenKey)
        }
        super.init()
    }

ahmedk92

        let queryParams = "{query}{&page, per_page, sort, order}"
        let urlString = "https://api.github.com/search/repositories?q=" + queryParams.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed)!
        let url = URL(string: urlString)!