Improving Composable Architecture Debugging


I’ve been a fan of Point Free Composable architecture for a while now.

I’ve worked on TCA projects for more than a year on projects of all sizes: from smaller projects like my indie Sourcery Pro, through the New York Times project, to a truly large codebase, a completely new browser for The Browser Company.

TCA has been working great in all of them, but one thing that I was missing was an easy way to debug state changes, as the official debug higher-order reducer doesn’t play well with large app states.

So I thought: let’s create an interface that will not only deal with larger states, but also offer us a way to filter actions with ease:

.debugDiffing(allowedActions: .allExcept(.hoverActions, .windowVisibility))

Apple Treats interview


Yesterday I was interviewed by Apple Treats

You can watch the recording here:

Or listen in Apple Podcasts

Dear Xcode....


Two weeks ago I’ve released Sourcery Pro, the most powerful Xcode extension that exists.

If you still didn’t check it out, you really should as it can save you 100+ hours by letting you automate a lot of repetitive code in your projects, from writing mocks through SwiftUI and Snapshots.

Now let me tell you a bit about what Xcode extension offer and a couple of ideas for what Xcode team could add in future releases, to make tools like Sourcery Pro more powerful.

Introducing Sourcery Pro


Today I’m happy to announce a new mac app that extends Xcode features.

This is an effort of over 1000 hours, so if there was ever time to show your support for all the open source work I’ve done, it’s now.

Read more

The Decade in Review


Lately, I’ve spent a significant amount of time thinking about my career: what I’ve done so far and what might lie ahead for me.

To gain some perspective, I’ve decided to journal some of the things I’ve done over the last decade, and to share that with you.

So below you will find some of my projects for the Cocoa community, as well as the highlights of commercial work I enjoyed and can talk about (NDA’s).

Improve build times by extracting 3rd party tooling to processing script.


A lot has been written about improving Swift compile times, but the compiler and linker are just part of the equation that slows down our development cycle.

Most projects leverage great 3rd party tools like SwiftLint, Sourcery, SwiftGen, SwiftFormat and many more. Leveraging those tools is the right thing to do but we have to be aware that all of those tools come with some time delay for our build -> run development cycle.

We often set those tools to run as build-phases which means they run each time you attempt a build but none of those tools need to be run each time we build.

Even tools that generate code we need for our projects like Sourcery or SwiftGen don’t need to be re-run unless we made changes in very specific parts of the application.

As an example New York Times main application leverages a lot of 3rd party and internal tooling, the total time all the tools take is 6s on my (powerful) machine.

Only 6 seconds or as much as 6 seconds? Let’s put this into context:

  • I build a project between 200-400 times on an average workday.
  • Let’s assume 90% of the time we don’t need to run those tools with each build.
  • We have 30 iOS developers working on the main app

Lower limit: 200 * 6s * 30 * 90* => 9 hours wasted per day

We are wasting 45 hours per week, if we can improve that it’s almost like hiring a new full-time developer, except it’s free.

Let’s look at how we can improve this with a process change a dash of bash shell programming.

Adding support for versioning and migration to your Codable models.


Codable is a great protocol for automating simple model persistence, but it lacks support for any kind of versioning or migrating the data from older versions.

You can, of course, implement custom Codable adherence and throw in a bunch of if statements and manual decoding to achieve this goal, but isn’t that kind of killing the main selling point of Codable?

Let’s look at an idea that adds Versoning yet still leverages derived Codable.

Straighforward Data Snapshots


If your app has a lot of content, chances are that by the time you get a chance to work on a bug report, the data that the bug appeared on will be long gone.

Here are some tidbits on how I created a simple solution for that problem at The New York Times, it’s based on a simple idea.

Finding exact difference between 2 instances


Have you ever written tests? Usually, they use equality asserts, e.g. XCTAssertEqual, what happens if the object isn’t equal? Xcode throws a wall of text at you:

This forces you to manually scan the text and try to figure out exactly whats wrong, what if instead you could just learn which property is different?



How to find retain cycles and memory leaks sooner


LifetimeTracker can surface retain cycle / memory issues right as you develop your application, and it will surface them to you immediately, so you can find them with more ease.

Instruments and Memory Graph Debugger are great, but too many times developers forget to check for issues as they close the feature implementation.

If you use those tools sporadicaly many of the issues they surface will require you to investigate the cause, and cost you a lot of time in the process.