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Latest weblog entries

2018-08-27 Two useful Xcode shortcut keys

I found out about two extremely useful Xcode shortcut keys: Ctrl+Cmd+[ or ] to cycle through the active target, and Ctrl+Option+Cmd+[ or ] to cycle through devices.

2018-05-15 Non-existing dates

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.

2018-03-16 overview of font sizes when using Dynamic Type

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/

2018-01-11 Navigationbar below statusbar on iOS 10

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
        }
    }

2017-12-23 Showing SVG image without libraries

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()

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