When barcodes attack — fixing PDF417 detection in Xcode 13

The bug 🐛

This past week I came across a fascinating bug, the kind I don't think I've encountered before. I'm working on a project where we use the [Vision framework][0] to detect [PDF-417 barcodes][1].

In order to do that we create a VNDetectBarcodesRequest with its symbologies set to PDF-417, like so:

When using the release candidate for Xcode 13 (build 13A233) which ships with the iOS 15 SDK and Swift 5.5 toolchain, there is now a warning saying that .PDF417 has been renamed to .pdf417.

However, if you change the symbol name to the new, lowercased version and try to run on an earlier version of iOS (e.g. iOS 13) this results in a crash at runtime:

SIGABRT: missing lazy symbol called

As you would expect, the lowercased symbol name works fine on devices running iOS 15.

The Workaround 🔨

Initially I thought, I'll wrap this in an @available conditional and the problem will go away. Shouldn't be necessary but it fixes the problem:

However, we're still using Xcode 12.5 on CI to build and test, and if this is an issue how many more monsters are out there?

It may be wiser to wait until Xcode 13.1 before moving to this new toolchain.

The band-aid 🩹

So to get the best of both worlds and ensure this works on both older and the latest versions of iOS, regardless of your choice of Xcode (limited to 12.5 or 13), I ended up going with the following:

It doesn't feel that clean, but it does work. 🤷‍♂️

 Feedback: FB9659813.

Automating iOS Simulator Screenshots With Pretty Good Status Bars Using Xcode 11

Yesterday I discovered a new command line tool (which ships with Xcode 11) that can clean up iOS Simulator status bars. It works great, but I have automated taking app screenshots using Fastlane and Snapshot — if you haven't you should check it out as its a massive time saver.

Unfortunately there is currently a bug where Snapshot apparently overrides or undoes the status bar change — there is however work underway to add support for this new feature.

Until then, I've come up with what I believe is a clumsy but acceptable workaround. 🤓

I don't want to take screenshots manually. After having used Snapshot for so many years now that seems like going back to the stone age and I already have my lovely UI tests in place to take the screenshots of exactly what I want.

Avoid Town isn't localized at the moment, so its only a case of taking screenshots at two locations on:

• iPhone SE
• iPhone 8
• iPhone 8 Plus
• iPhone Xs
• iPhone Xs Max
• iPad
• iPad Pro (3rd gen)

That's 2 screenshots for each devices, so 2 * 7 = 14 screenshots. And then I want to take the same screenshot but in dark mode so 28 screenshots in total.

If there were more languages supported that would be 28 per language and you can see that this quickly becomes untenable. So I am going to continue to use Snapshot.

My workaround is as follows, in one Terminal I run fastlane snapshot as normal.

However in a second Terminal I run the following:

while sleep 1; 
do xcrun simctl status_bar 'iPhone SE' override --time '9:41' --dataNetwork 'wifi' --batteryState 'charged' --cellularMode 'notSupported' --wifiMode 'active' --wifiBars 3; 
done

Basically I override the status bar on a particular device every second 😱. This ensures that it also happens while Snapshot is running.

Yep, I know its gross 🤢. And it also means I have to take snapshots of one device at a time. Then I have to stop the script, change the name of the device, and run Snapshot again for that device. Like an animal.

You could of course modify all the Simulators you're targetting in your Snapfile by adding multiple do lines to the while block above, but I did them one by one to verify that the process worked.

The upside is that its mostly automated and because I only have to do it 7 times (for this release) I can live with it. My hope is that by the time I have to do this again the Snapshot issues linked to above will be fixed 🤞

Below is an example of the output created by Snapshot.

Screenshots exported via Snapshot

Making perfect Pretty Good iOS Simulator status bars with Xcode 11

This morning I've been updating the screenshots for the latest update of Avoid Town which adds among other things support for Dark Mode on iOS 13.

I've been using Simulator Status Magic for as long as I can remember to clean up the status bar — this involves removing the Carrier name, setting the battery to 100% and full bars. For some reason this wasn't working, so I started looking into it and found the following:

Xcode 11 beta 4 includes support for perfect status bars without SimulatorStatusMagic! 🎉 Run xcrun simctl status_bar with beta 4 or later installed and rejoice! This project will be going away soon, which is great news.

Looks like the time has finally come to wave goodbye to Simulator Status Magic. Its been a great run and you served us well, thank you for your service 👋😄

The xcrun simctl status_bar tool allows us to override the status bar with several options:

time <string> Set the date or time to a fixed value. If the string is a valid ISO date string it will also set the date on relevant devices.

dataNetwork <string> If specified must be one of 'wifi', '3g', '4g', 'lte', 'lte-a', or 'lte+'.

wifiMode <string> If specified must be one of 'searching', 'failed', or 'active'.

wifiBars <int> If specified must be 0-3.

cellularMode <string> If specified must be one of 'notSupported', 'searching', 'failed', or 'active'.

cellularBars <int> If specified must be 0-4.

batteryState <string> If specified must be one of 'charging', 'charged', or 'discharging'.

batteryLevel <int> If specified must be 0-100.

My first attempt was the following:

xcrun simctl status_bar 'iPhone 11' override --time '9:41' --dataNetwork 'lte' --batteryState 'charged' --cellularMode 'active'

This sets the time to 9:41, using LTE with a full battery. This looks great on iPhone X and later.

Cleaned up status bar on iPhone X

However, on older devices this still shows the Carrier name.

Carrier name visible on iPhone 8

I really dislike showing the Carrier name and it doesn't look like there is a way of removing it using simctl override, so instead I opted for the following:

xcrun simctl status_bar 'iPhone 11' override --time '9:41' --dataNetwork 'wifi' --batteryState 'charged' --cellularMode 'notSupported' --wifiMode 'active' --wifiBars 3

This sets the time to 9:41, using Wifi with a full battery.

Carrier name now longer visible on iPhone 8

Cleaned up status bar on iPhone X, now using WiFi

Personally I prefer showing LTE and bars, but this doesn't appear to be possible without also showing the Carrier name which seemingly we can't remove so this is a fine compromise.

Another option is to vary what we do depending on if the device has a notch or not. I'm currently trying to figure out how to automate this with Fastlane.

Update (Sep 18, 2019): I wrote about how I automated this with Fastlane / Snapshot here.

Moving to SF Symbols

I'm slowly working on replacing existing assets with SF Symbols wherever possible in this app I'm working on. In order to maintain a consistent look on iOS 12 and below I'm replacing the existing 1/2x/3x PNGs with a single PDF, by exporting the SVG from the SF Symbols app into Sketch.

By naming the bundled assets the same as the system names, I can use this handy extension to avoid the "if available" dance every time:

At first I wasn't sure if I wanted to update the older assets, but I think I prefer a consistent look regardless of iOS version even if it does mean a bit of extra work. Moving to PDF assets also means less files to update and hopefully a smaller app size.

I ❤️ cocoapods-binary

I've been using Cocoapods for dependencies for as long as I can remember. Personally I never really got along with Carthage, but some people prefer it.

Over the weekend I came across a post titled "Using CocoaPods with pre-built frameworks instead of source files" which has radically decreased the build time on some of my projects. It describes how you can set up the cocoapods-binary plugin to precompile your dependencies which dramatically reduces the amount of time Xcode needs to build your app.

In two small-to-medium sized apps with 5-10 dependencies I saw upto 10x improvements. A clean build (with nuked derived data) going from about 90 seconds down to 9. 🤯🤯🤯

If you're using Cocoapods you really should try it out.