Scott Berrevoets - til

Objective-C enums can be string-backed... sort of

2026-04-24T00:00:00-07:00

While looking at AVAudioSessionErrorCode in Xcode, I noticed something interesting in its definition:

typedef CF_ENUM(AVAudioInteger, AVAudioSessionErrorCode) {
    AVAudioSessionErrorCodeNone = 0,
    AVAudioSessionErrorCodeMediaServicesFailed = 'msrv',   // 0x6D737276, 1836282486
    AVAudioSessionErrorCodeIsBusy = '!act',                // 0x21616374, 560030580
    AVAudioSessionErrorCodeIncompatibleCategory = '!cat',  // 0x21636174, 560161140
    AVAudioSessionErrorCodeCannotInterruptOthers = '!int', // 0x21696E74, 560557684
    AVAudioSessionErrorCodeMissingEntitlement = 'ent?',    // 0x656E743F, 1701737535
    AVAudioSessionErrorCodeSiriIsRecording = 'siri',       // 0x73697269, 1936290409
    AVAudioSessionErrorCodeCannotStartPlaying = '!pla',    // 0x21706C61, 561015905
    AVAudioSessionErrorCodeCannotStartRecording = '!rec',  // 0x21726563, 561145187
    AVAudioSessionErrorCodeBadParam = -50,
    AVAudioSessionErrorCodeInsufficientPriority = '!pri',  // 0x21707269, 561017449
    AVAudioSessionErrorCodeResourceNotAvailable = '!res',  // 0x21726573, 561145203
    AVAudioSessionErrorCodeUnspecified = 'what',           // 0x77686174, 2003329396
    AVAudioSessionErrorCodeExpiredSession = '!ses',        // 0x21736573, 561210739
    AVAudioSessionErrorCodeSessionNotActive = 'inac',      // 0x696e6163, 1768841571
};

The technique Apple used in defining the values of this enum is called FourCC, short for "four-character code". They are multi-character constants in C, but they are not strings; they're integers created from the ASCII bytes of each character. The comment after each value is the combined hex value of the integer followed by that same value in base 10.

For AVAudioSessionErrorCodeMediaServicesFailed:

m = 0x6D
s = 0x73
r = 0x72
v = 0x76

0x6D737276 = 1836282486

The limitation is 4 ASCII characters, but with some creativity you can get pretty far: siri is obvious, msrv is short for "media services", and !rec means "not recording". I particularly like what for an unspecified error.

These strings are especially useful while printing/logging, since you can get the four-character code printed using printf("%.4s", (char*)&error);. It's no longer relevant to us in a Swift world where all of this is much easier, but still a neat piece of history I learned more about.

`Optional` has a `take()` function

2026-04-05T00:00:00-07:00

After the introduction of Optional.toggle() back in 2018, I thought I had learned everything there is to Optional, but today I learned about another method: Optional.take(). As the [documentation] points out, it returns the value of a mutable optional (if not nil) and then resets the variable to nil:

var myInt: Int? = 42
var myOtherInt = myInt.take() // 42
print(myInt) // nil

Because this also works if myInt was nil, take() returns an optional as well. Nothing groundbreaking, but could save you an occasional line of code.

Claude can load files "lazily" or "greedily"

2026-03-20T00:00:00-07:00

Typically, markdown files can referenced other files by linking to them: [My File](myfile.md). Claude understands this syntax, making it a nicely portable way to reference files. When prompting in Claude Code, referencing other files works through the @-syntax: @path/to/file. This loads the file into Claude's context similar to the markdown linking.

When Claude sees the @-syntax in a markdown file, it reads it as well. But Claude doesn't treat the markdown and @ syntaxes as equals: linking to a file may cause it to read that file when it feels like it's the right time for it. The @-syntax will immediately and unconditionally inline that file into the prompt.

In short, the markdown linking syntax is akin to "lazy loading", whereas the @-syntax is "greedy loading".

macOS can remember SSH passphrases

2026-03-02T00:00:00-08:00

Having to type out my password every time in SSH into a machine got a little tedious for me. Turns out macOS can save these passphrases to the Keychain to save some typing each time you try to connect to a host over SSH.

To enable this, make sure you're using the macOS-native ssh version. I had a homebrew version installed, which doesn't support this. Verify with which ssh, which should output /usr/bin/ssh.

Then run the following:

# Add private key to Keychain
ssh-add --apple-use-keychain ~/.ssh/id_ed25519

# SSH config to read from Keychain
echo "Host *
    UseKeychain yes
    AddKeysToAgent yes
    IdentityFile ~/.ssh/id_ed25519" >> ~/.ssh/config

This is enough to make it work one-time, but to preserve this option across reboots add the following line to your ~/.zshrc:

ssh-add --apple-load-keychain -q

Now SSH works without having to enter a passphrase or password again. In theory this also works with RSA keys, but not all modern servers support that for security purposes. Try an ed25519 key instead if the steps above don't work with an RSA key pair.

git can tell you ignored files, and why

2026-02-10T00:00:00-08:00

Today I created a new file at ./Resources/Environment.xcconfig, but git didn't pick up on the file and didn't show it in git status. I suspected the file was gitignored, but nothing in my .gitignore was obviously excluding this file. git status --ignored adds a section in to the normal status output that lists all the ignored files. My file was in it, but I still didn't know why.

git check-ignore as a bare command confirms the ignored status of the passed in file, but adding the -v flag indicates the source of the ignore. I ran git check-ignore -v Resources/Environment.xcconfig and the exact line number in gitignore showed what caused the file to be ignored.

In my case, a different Environment.xcconfig existed before and had been removed from the repo, but not from gitignore so it caused the new file to be ignored as well.

There is a term for words like i18n and a11y

2026-01-27T00:00:00-08:00

They're called numeronyms and they're common terms in tech to refer to long words like "internationalization" (i18n) and accessibility (a11y). However, they're also used outside of tech: K9, 24/7, and gr8 are all numeronyms as well.

The official definition, according to Wikipedia:

A numeronym is a word, usually an abbreviation, composed partially or wholly of numerals.