Ancient Secrets of the Objective-C Runtime

Applied ObjC for modern Swift apps

Don’t go anywhere! Seriously.

This is not some theoretical archaeological deep-delve.

I’m going to give you something you can use in your Swift apps today.

I’m NOT talking about #selector, @objc-marked methods, or dynamic functions.

This post is about Objective-C runtime internals. How ObjC is built, the powerful features it offers, and how to apply these features to simplify your modern Swift codebase.

---

I’ve been doing iOS for just under 10 years. I went into consulting in 2016, just after the Grand Renaming™ of Swift 2.0 to Swift 3.0.

It was kind of an annoying time to begin tbh.

I spent month #1 of my first ever job working through the Big Nerd Ranch Swift textbook, but Deloitte didn’t want to shell out $21 for the Swift 3 edition, so I spent half my time Googling each line of syntax to find the renamed version.

I dipped my toe into a few hairy legacy ObjC codebases back in the day, but I’ve managed to spend about 98% of my career rolling Swift. Yay me.

Most iOS devs today are similar. Many of you have likely never touched Objective-C.

So why am I darkening your doorstep with a d̵͈͚̈́́̑e̴͙͐̍ä̶̠̺̣́͆́d̸̳͠ ̵̰͉̾̓l̵͚̬͆͂́ā̵̧̛̼̈́ǹ̸̡͎̟̔g̶̣̜̋̊̃u̷̙̇̂͗ą̸͉͕͘͝͝g̶̢̞̈̀e̷̫͔̿?

3 reasons:

• We can learn a lot from ObjC’s design and runtime internals.

• There are useful practical applications that work in UIKit apps today.

• It’s really bloody interesting.

Sound good? Come along for the ride.

• A (very) brief history of Objective-C

• What makes Objective-C special?

• The ObjC Runtime

• objc_msgSend and Message Dispatch

• The power of the runtime

• Modern Practical Applications

  • Screen tracking and Swizzling

  • Tracking dwell time with Associated Objects

  • Active screens and introspection

  • Interacting with collections via Message Forwarding and NSProxy

• Last Orders

Upgrade to unlock this article, plus much more:

🌟 Access Elite Hacks, my exclusive advanced content
🚀 Read my free articles a month before anyone else
🧵 Master concurrency with my course and advanced training