Fastlane

Fastlane is mostly pretty great, automating much of the drudgery around releasing apps, but there are issues with Xcode’s UI testing where the simulator will fail to launch with UI Testing Failure - Timeout waiting to launch Target Application. or UI Testing Failure - App state is still not terminated. errors, especially with a large number of UI Tests (Trail Wallet has over 35).

This means that one of the big ticket items of Fastlane, Snapshot, is unreliable with my full test suite. However, I didn’t want to give up on it because the idea of having a process that automatically takes and uploads screenshots to iTunesConnect for all devices across multiple locales based on the current version of the app was just too good to leave behind.

In the end, in order to get reliable results, I ended up duplicating my main scheme and simply removing all other UI Tests, leaving only tests specifically designed for Snapshot. It’s defiling the sanctity of my tests to have tests specifically to take screenshots, of course, but the potential time saving benefits are well worth it and, hopefully, it’s only temporary.

Here’s how I did it:

1. Click the app icon to get access to the Scheme menu, then click ‘Manage schemes…’

Screenshot showing how to access the scheme manager in Xcode

    2. Select your main app scheme, then down in the bottom left click the gear icon and click “Duplicate”

    Screenshot of the scheme options menu in Xcode

    3. Rename your scheme (e.g. <AppName>Snapshot) then click “Edit…”

    4. Click on Test in the left hand list, then click the disclosure indicator next to your UI Tests target and deselect everything except your snapshot tests.

    Screenshot showing how to edit the Test target of the new scheme in Xcode

    5. Finally, (assuming Fastlane is set up in your application folder) edit your Snapfile at [AppDir]/fastlane/Snapfile and set the scheme to your newly created scheme:

    Snapshot will use this new scheme and only run the relevant tests.

    It’s not ideal, as having Snapshot run through every test and verify they pass on every device before uploading a build is good practice, but given the unreliable nature of the simulator for me at the moment this at least gets me some of the benefits of using Snapshot.

Redefining Symbol Error and Core Data Entities

I have had modules switched off in Xcode for Trail Wallet since its introduction. I have a Core Data entity called “Category” and, when I tried to enable the modules feature (introduced in Xcode 5), I was hit with Redefinition of 'Category' as a different kind of symbol error.

Recently, however, things came to a head when I tried to import a mixed-source framework into Trail Wallet and it refused to see the Swift files.

The solution to getting Swift files in external frameworks to work in Objective-C projects, according to Apple’s Using Swift with Cocoa and Objective-C, is to import it as a module within Objective-C (e.g. @import ExternalFramework;).

So I assumed I was finally going to have to tackle entity renaming, which is handled by Core Data’s lightweight migration but only if it is set up correctly.

I generally dislike database migrations and try to avoid doing them if I can. I’ve never had an issue with a production version and migration (probably because I’m so paranoid about it), but it’s always nerve-wracking when a new version with a migration goes out into the world.

Previous searches had yielded no good news but I thought I should search one last time, which revealed this answer at Stack Overflow—I could avoid a migration after all.

The SO answer is a little light on details, so here are the exact steps I took:

1. Select the .xcdatamodeld file, then select the entity that’s causing the conflict (Category, in my case)

2. Select the Data Model inspector in the Utilities pane.

3. Rename the Class property:

A screenshot showing where to set the class name for a Core Data entity.

4. Re-generate the NSManagedObject subclasses by going to Editor -> Create NSManagedObject Subclass....

Xcode 7’s NSManagedObject subclasses work a little differently than they used to—it generates its own category that it is then free to overwrite should you change the entity in future versions, and leaves the core class for you to add additional methods and properties to.

5. If you have added additional functionality to the NSManagedObject subclasses, you’ll need to copy it across.

I had a category on my Category entity (of course I did) called Category+GetCategories.[h/m], so I had to copy out all of the API and implementation from these files and put it all in the newly generated CDCategory.[h/m] files.

6. Delete the old classes.

7. Update all references to the old class and replace them with the new class, in my case I had to replace Category and with CDCategory throughout the project.

It all worked just fine, no database migration or entity renaming required.

The only other gotcha was that, after attempting to run with the new framework, it was crashing out with a dyld: Library not loaded: @rpath/libswiftCore.dylib error.

This is caused by the build setting Embedded Content Contains Swift Code being set to No. Switching this to Yes allowed the project to run and use the Swift code in the framework.

Useful CGFloat Extensions

I’ve been working a lot with CALayers over the past few days, specifically layers with circular shapes, and so these two little extensions have been really useful.

The first is your standard degrees to radians conversion function that every programmer that’s worked with UI has probably written at some point.

The second is a bit more interesting, though, as it finds a point on a circle within a frame of a given size (it also assumes that 0 is the top of the circle, not the right edge as in Core Animation):

Model Decisions

I’m about to get started on a new iOS app and the first major decision is what form the model is going to take.

The app will be a quiz style app where my client will be providing the questions in the form of a large JSON file.

Initially I was going to create individual model objects, have a questions manager object read in the JSON file on launch and create the various question objects, along with their parent containers. The question tree is relatively complex, with each question sitting under three ancestor nodes.

In terms of persistence, the only things that I need to keep track of is how many times a user has attempted a question and whether or not they were correct on the last attempt.

Initial Idea

My initial idea was to have a questionManager, together with various model objects. The Question objects would vend an array of Answer objects. The controller would then pass back an array of Answer objects to the Question object which would update its state and return a tuple consisting of a Bool and an NSAttributedString object indicating whether or not the answer was correct, and giving more information about the correct answer.

This would work fine and persistence would be relatively straightfoward. After the initial read of the JSON file (which will run to around 2,000 questions), I would just have all the model objects conform to NSCoding and freeze and unfreeze the questionManager between launches.

Core Data?

Trail Wallet uses Core Data to manage its data and I am very happy with it. Xcode features a decent model editor and between NSPredicate, NSFetchRequest, and NSFetchedResultsController I get a lot of power and convenience for free, not to mention that persistence is straightforward.

I haven’t yet branched into iCloud for Trail Wallet, but it is something that I am eager to implement and (if it works well—which is a big "if", given iCloud Core Data’s history) then I’ll get a lot of syncing power for very little effort (as opposed to a third party solution, or even just having to manage mapping the model to CloudKit).

Implementing Core Data in this new app which, admittedly, is overkill for something so straightforward would allow me to try out iCloud Core Data with very little risk.

All user data loss is bad, but losing the history of which questions were answered seems a lot less catastrophic than years worth of financial records. I would also get some experience in managing migration paths when iCloud is in play before I implemented it in our most important app.