One William Woodruff wrote a blog entry in 2015 about non-existing dates: https://blog.yossarian.net/2015/06/09/Dates-That-Dont-Exist
I'm sad to say that Foundation allows you to construct these supposedly illegal Gregorian dates :(
import Foundation
var dateComponents = DateComponents()
dateComponents.day = 6
dateComponents.month = 10
dateComponents.year = 1582
dateComponents.timeZone = TimeZone(abbreviation: "UTC") if let date = Calendar(identifier: .gregorian).date(from: dateComponents) {
print(date)
} else {
print("Not a date")
}The above Swift code can be pasted into a playground. Supposedly, it shouldn't print the date but it does. This is a pretty obscure corner case of course.
If you want to support Dynamic Type in your iOS app, and I think you should, then one possible route is to roughly map the built-in text styles to the point sizes that your design specifies. The following page on the Apple website lists all text styles along with their point size:
https://developer.apple.com/ios/human-interface-guidelines/visual-design/typography/
I had the strangest issue today. When testing my current app on iOS 10, the navigation bar would sit below the status bar. In other words, the navigation bar would be 44 pixels high, instead of 64 pixels. On iOS 11, this issue wasn't present.
This happened because our app does not use storyboards, and we used the following AppDelegate.swift:
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {var window: UIWindow? = UIWindow(frame: UIScreen.main.bounds)
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
let mainViewController = ViewController()
let navigationController = UINavigationController(rootViewController: mainViewController)
self.window?.rootViewController = navigationController
self.window?.makeKeyAndVisible()
return true
}}
The problem is, that the window property is initialized too early. Moving it to didFinishLaunching fixes the problem:
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {var window: UIWindow?
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
self.window = UIWindow(frame: UIScreen.main.bounds)
let mainViewController = ViewController()
let navigationController = UINavigationController(rootViewController: mainViewController)
self.window?.rootViewController = navigationController
self.window?.makeKeyAndVisible()
return true
}}
Recently I had the need to show a logo in SVG format, but the project required that we did not include 3rd party libraries. The following Swift playground shows how you can show an SVG-based image using WKWebView.
Somehow, you need to know the image size beforehand -- or at least you need to be able to set width and height constraints. Lots of logos are square, thus there's no need to do anything special.
import UIKit
import PlaygroundSupport
import WebKit class MyViewController : UIViewController {
override func loadView() {
let view = UIView()
view.backgroundColor = .white let webView = WKWebView()
webView.translatesAutoresizingMaskIntoConstraints = false let header =
"""
<!DOCTYPE html><html style=\"overflow: hidden\">
<head>
<meta name="viewport" content="initial-scale=1.0" />
<title>icon_people_search</title>
</head>
<body style=\"margin: 0;\">
"""
let footer =
"""
</body>
"""
let svg =
"""
<?xml version="1.0" encoding="iso-8859-1"?>
<!-- Generator: Adobe Illustrator 19.0.0, SVG Export Plug-In . SVG Version: 6.00 Build 0) -->
<svg version="1.1" id="Layer_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
viewBox="0 0 495 495" style="enable-background:new 0 0 495 495;" xml:space="preserve">
<g>
<polygon style="fill:#1A6FB0;" points="247.5,0 247.5,40 455,40 455,455 247.5,455 247.5,495 495,495 495,0 "/>
<polygon style="fill:#1E81CE;" points="40,455 40,40 247.5,40 247.5,0 0,0 0,495 247.5,495 247.5,455 "/>
<path style="fill:#1E81CE;" d="M205.767,405h65.266V247.413h43.798c0,0,4.104-25.428,6.103-53.235h-49.647v-36.264
c0-5.416,7.109-12.696,14.153-12.696h35.564V90h-48.366c-68.478,0-66.872,53.082-66.872,61.009v43.356h-31.771v53.029h31.771V405z"
/>
</g>
</svg>
"""
webView.loadHTMLString(header + svg + footer, baseURL: Bundle.main.bundleURL)
view.addSubview(webView)
let constraints = [
webView.widthAnchor.constraint(equalToConstant: 100),
webView.heightAnchor.constraint(equalToConstant: 100),
webView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
webView.centerYAnchor.constraint(equalTo: view.centerYAnchor)
]
view.addConstraints(constraints)
self.view = view
}
}
// Present the view controller in the Live View window
PlaygroundPage.current.liveView = MyViewController()On iPhone, you usually add a cancel/close button to a modal popover. On iPad, there's usually no need to do so. Users just tap outside the popover to dismiss it. However when you're building an app for the iPad, and you support Split View and Multitasking, you suddenly do need it.
The following viewcontroller will display a popover, and if necessary a close button will be added.
class PresentingViewController: UIViewController, UIPopoverPresentationControllerDelegate {
// MARK: - UIPopoverPresentationControllerDelegate
func adaptivePresentationStyle(for controller: UIPresentationController) -> UIModalPresentationStyle {
return .fullScreen
}
func presentationController(_ controller: UIPresentationController, viewControllerForAdaptivePresentationStyle style: UIModalPresentationStyle) -> UIViewController? {
guard let navigationController = controller.presentedViewController as? UINavigationController else {
fatalError("Unexpected type of controller")
}
let closeButton = UIBarButtonItem(title: "Close", style: .done, target: self, action: #selector(close))
navigationController.topViewController?.navigationItem.leftBarButtonItem = closeButton
return navigationController
}
@objc func close() {
self.dismiss(animated: true, completion: nil)
}
// MARK: - View cycle
@objc func popoverAction() {
let pvc = PopoverViewController()
let navigationController = UINavigationController(rootViewController: pvc)
navigationController.modalPresentationStyle = .popover
navigationController.popoverPresentationController?.delegate = self
navigationController.popoverPresentationController?.sourceView = self.view
navigationController.popoverPresentationController?.permittedArrowDirections = .up
navigationController.popoverPresentationController?.sourceRect = CGRect(x: 40, y: 40, width: 1, height: 0)
self.present(navigationController, animated: true, completion: nil)
} override func viewDidLoad() {
self.view.backgroundColor = UIColor.yellow let barButtonItem = UIBarButtonItem(title: "Popover", style: .plain, target: self, action: #selector(popoverAction))
self.navigationItem.leftBarButtonItem = barButtonItem
}
} class PopoverViewController: UIViewController {
override func viewDidLoad() {
self.view.backgroundColor = UIColor.green
}
}For historic accuracy, below you can find the manual solution. It's mainly obsolete.
class PresentingViewController: UIViewController {
private var popoverViewController: PopoverViewController?
override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
self.popoverViewController?.doneButtonHidden = (self.traitCollection.horizontalSizeClass == .regular)
}
@objc func popoverAction() {
let pvc = PopoverViewController()
pvc.doneButtonHidden = (self.traitCollection.horizontalSizeClass == .regular)
let navigationController = UINavigationController(rootViewController: pvc)
navigationController.modalPresentationStyle = .popover
navigationController.popoverPresentationController?.sourceView = self.view
navigationController.popoverPresentationController?.permittedArrowDirections = .up
navigationController.popoverPresentationController?.sourceRect = CGRect(x: 40, y: 40, width: 1, height: 0)
self.present(navigationController, animated: true, completion: nil)
self.popoverViewController = pvc
}
override func viewDidLoad() {
self.view.backgroundColor = UIColor.yellow
let barButtonItem = UIBarButtonItem(title: "Popover", style: .plain, target: self, action: #selector(popoverAction))
self.navigationItem.leftBarButtonItem = barButtonItem
}
} class PopoverViewController: UIViewController {
var doneButtonHidden: Bool = false {
didSet {
let button = UIBarButtonItem(barButtonSystemItem: .done, target: self, action: #selector(dismissAction))
self.navigationItem.leftBarButtonItem = self.doneButtonHidden ? nil : button
}
}
@objc func dismissAction() {
self.dismiss(animated: true, completion: nil)
}
override func viewDidLoad() {
self.view.backgroundColor = UIColor.green
}
}This works, but requires that you keep a reference to the PresentedViewController, to update the visibility of the close button. I don't much like having a class member variable when it could be a local variable, because it clutters up the code of the PresentingViewController. But this is the most concise and readable code I could come up with.
Note that when you use child ViewControllers, this does not seem to work. The reason is that traitCollectionDidChange() doesn't get called automatically. In that case, it could be acceptable to use viewDidLayoutSubviews().
Articles, chronologically (latest first). This is pretty old stuff.
Not yet finished. Maybe will never be finished. Maybe they'll get deleted. Who knows?
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