Do you know this trick to spot memory leaks? 🤨

Hi 👋

It’s been quite a busy and exciting week-end for me: I’ve listed something for sale on Gumroad for the first time ever!

Today is a bank holiday in France, and I’m quite happy I have this extra day off to settle down and rest a bit 😌

But before I go enjoying my day off I want to share a pretty cool trick with you, that should help you notice more easily when a ViewController starts to leak from memory!

This trick relies on a clever use of a feature in Xcode called Symbolic Breakpoints.

What is a Symbolic Breakpoint you might be wondering?

It’s quite similar to a regular breakpoint, except that its triggering mechanism isn’t linked to a line of code being executed, but rather to a method being called.

First, let me show you how to create a Symbolic Breakpoint in Xcode:

Then, the next step is to set the symbol that will trigger the breakpoint:

At this point, there’s a good chance that you might be wondering where this weird syntax comes from: -[UIViewController dealloc]

It actually comes from Objective-C!

Let me break it down for you:

• “-” indicates that we’re dealing with an instance method

• “[object method]” is the Obj-C syntax for a method call

• “UIViewController” is the type we want to monitor

• “dealloc” is the Obj-C equivalent to “deinit” in Swift

This means that were are defining a Symbolic Breakpoint that will trigger whenever an instance of UIViewController (including its subclasses) gets released from memory 👍

After that, let’s add an action to this breakpoint:

I’ve added an action that will play a sound whenever the breakpoint is triggered. 🎶

To finish, I check the box so that the breakpoint will only execute its action and won’t actually stop the execution flow:

So what have we managed to achieve with this Symbolic Breakpoint?

We’ve basically created a nice mechanism that will play a sound whenever a ViewController gets released from memory!

This should make it easier to spot a ViewController leaking from memory: whenever you pop the navigation stack or close a modal, if you don’t hear the little sound then you’ll know there’s probably a memory leak in your code 🐛

(Of course, you can totally replace the little sound by a console print, if that works better for you 👍)

If you’re curious to see a demo of this trick in action, I can recommend you watch this video I made last year:

That’s all for this email, thanks for reading it!

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I wish you an amazing week!

❤️