Nerd Fun Programming

Code Markup in Xcode

I’m working on a fairly large Swift project. Actually no, that’s not quite true. I’m working on a Swift project with a ViewController file that is getting disorganized and out of control. If this keeps up I might have a large project on my hands but right now it’s just a single file that is getting larger than I would like.

Apple provides some quick and dirty tools that make it easy to navigate a single file with specially formatted comments in your code. This functionality doesn’t provide automated documentation like Headerdoc. And that’s fine with me. I like how Headerdoc has become a mash up of Markdown and JavaDoc. My code is just not stable enough for documenting yet.

Happily Xcode’s built-in special comment parser is enough in the early stages of development to help me navigate a large file and remember where the bodies are buried.

Xcode supports the following out of the box:

  • MARK: (your text here)
  • MARK: – (section divider)
  • ???: Question
  • !!!!: Warning
  • TODO: Task
  • FIXME: Bug

Xcode’s special comments mark up the function navigation  pop-up menu so that you can find your questions, warnings, tasks, and bugs in your code without a overtaxing your the private neural network in your skull. Unfortunately you can’t add new special comments and they don’t show up in the Symbol Navigator.

(Using the MARK: comment you can simulate adding your own special comments. MARK: doesn’t add the word MARK: in front of navigation items in the way that the other special comments do (TODO, FIXME, etc.). So you can use MARK: NOTE to navigate to notes in your Swift code if that makes you happy.)

I use the following additional special comments to keep my code organized and consistent. (Xcode will just ignore them unless I prefix each with MARK:)

  • NOTE: (when the function name is not enough)
  • HINT: (a non-obvious reminder about a bit of code)
  • DBUG: (end of line comment marking code that probably should be removed eventually)
  • DEMO: (example usage)
    // MARK: -
    // MARK: Storyboard Actions

    @IBAction func rightSwipeGesture(sender: UISwipeGestureRecognizer) {
        // HINT: previous page
        currentTrainIndex -= 1
        if currentTrainIndex < 0 {
            currentTrainIndex = trainCount - 1

    @IBAction func leftSwipeGesture(sender: UISwipeGestureRecognizer) {
        // HINT: next page
        currentTrainIndex += 1
        if currentTrainIndex == trainCount {
            currentTrainIndex = 0

It would be nice if Apple allowed us to personalize code markup in Xcode. But only after search and ranking in the App Store are fixed and a 1000 other higher priories are done!