One of the "Things I Don't Know" in the iOS ecosystem is Metal. As such, I've been working through Metal By Example recently, which still stands as a great introduction to Metal...

In the wild world of 2019 SwiftUI development, lots of things aren't documented. One such thing I ran into recently was the usage of RelativeDateTimeFormatter in a Text view...

I wrote previously about a technique I use in Trestle and CIFilter.io to support iOS 12 and lower while still using system provided, dark-mode accessible colors...

I've encountered this bug enough times that I figured it was time to write a quick post about it. If you've looked into multiple window support for your app in iOS 13, you might know that a lot of the setup you used to have to do in the app delegate now lives in the scene delegate instead...

In this post we'll look at a very specific but tricky interaction in UIKit, one which took me multiple days to work out how to implement. It's two view controllers of different sizes, pushed on a UINavigationController, which is presented as a popover. The view controllers...

For some reason lately, I've been having a lot of trouble installing apps and running tests in the iOS simulator on Xcode 10 (non-beta). The error message looks like this...

At the beginning of June, I launched sfsymbols.com since there wasn't a reference available on the web for searching and filtering the list of 1500+ system icons included in...

I'm a Docker noob, and for whatever reason, I can never remember the best way to do things with Docker, whether it's checking which containers are running or starting/stopping them. Putting some common commands here mostly for personal reference. List containers...

At WWDC 2019, Apple announced that Dark Mode would be supported on iOS 13. There are some significant changes to UIKit in order to support this - many of them are detailed in the talk Implementing Dark Mode on iOS which I'd highly recommend watching...

Pop quiz: in a UIButton, how do you set a padding of 10pt between the image and the title? I had to do this at work recently, and I was surprised at how hard it was to reason about. There are several posts talking about this topic (including this one which uses edge insets to flip the title and image!), but the answer for my use case was pretty hard to find...

About a year ago I wrote a puzzle game called Trestle. If you download it using any of the links in this post (by clicking on them on your iOS device), you'll get a nice Easter egg and two of the (normally paid) level sets enabled for free...

Today I'm launching CIFilter.io 🎉 CIFilter.io is a project I've been working on for the last few months, and today it's open source. It has two parts...

For my current side project, I have to export CIFilter parameters to json, and I've been running into issues with various CoreImage types not conforming to Swift's Codable...

At the most recent Swift Language User Group meetup, Patrick Barry presented a great talk about how Lyft implements dependency injection. I'd highly recommend watching the video - I was impressed by how clean and...

After struggling for some time with CIFilter documentation at work, I've been working on an app which can apply filters interactively for various inputs...

I've been working on a side project for better CIFilter documentation lately, and I decided this was as good of a time as any to try out RxSwift. We use reactive programming at work, but I haven't really been able to dig into it yet...

Another MacOS and another struggle through installing nokogiri. Most places online recommend using...

While building this site in Gatsby using MDX, I noticed that there wasn't any documentation on how to include data from the frontmatter of an MDX document in the document's page layout...

I use Gatsby as a static site generator to build this blog using React. As part of this, I wanted a simple component to display a static image, something like this:

<Image filename="myimage.png" />

Surprisingly, this is hard to do in Gatsby. The default Image component generated by Gatsby uses StaticQuery:

To clear a value from UserDefaults, I previously thought it was fine to do something like this:

UserDefaults.standard.set(nil, forKey: "myKey")

Turns out that this works differently in different iOS versions. Starting in iOS 11, setting nil for a key works as I expected.

There are some times in Swift, like when using System Trace, that you want to get the pointer value of an object directly as a UInt (passing the pointer to kdebug_signpost is one). I was surprised at how hard it was to find documentation on how to get a Swift reference’s pointer value as a UInt.

Swift can be tricky sometimes. For example, what does the following print?

class A: NSObject {
  let x: Int

  init(x: Int) {
    self.x = x
  }
}
func ==(left: A, right: A) -> Bool {
  return left.x == right.x
}
print(A(x: 1) == A(x: 1))
print([A(x: 1)] == [A(x: 1)])

Let's talk about syntax trees. In static analysis, a common operation is to take a character string (e.g. "x = 1") and transform it into well structured data. Let's try to do this in python. We'll use Pyparsing as our tokenization tool.

Ambitious, subject to change, incomplete, based on this. 1. Create something that touches 10,000 people. (January 20th, 2013) 2. Create something that touches 100,000 people. (January 14th, 2015) 3. Create something that touches 1,000,000 people.

Let’s talk about HTML tables. Here’s some code:

<table class="main">
  <colgroup><col class="votes"><col></colgroup>
  <tr>
    <td>Votes</td>
    <td>Comments</td>
  </tr>
  <tr>
    <td>
      <p class="vote-desc">Some long name, really long, like really super long</p>
      <p class="vote-desc">Another long name, really long</p>
    </td>
    <td>
      <p class="comment">A really, really, really, really, really really really really really, really long comment.</p>
    </td>
  </tr>
</table>