Competitive programming is a great way to master a specific programming language. Even if you're not interested in competing in world events like the Facebook Hacker Cup, tackling difficult algorithm problems using nothing but the language's bread and butter will expose you to aspects/shortcuts of the language you would otherwise never see, such as how efficient certain methods/operations are and how to code better alternatives.

It's very common to use the weak keyword in order to prevent reference cycles in properties like delegates.

Unfortunately, since it protects you from references being lost, it forces the usage of var and an optional type, which can be quite jarring if you're building something like an UIView that is not supposed to be used without a delegate - much less change delegates suddenly. The unowned keyword allows you to overcome these issues.

It's very likely that you asked yourself at least once in your iOS career what's the difference between a struct and a class. While realistically the choice between using one or another always boils down to value semantics versus reference semantics, the performance differences between the two are expressive and can heavily favor one or another depending on the contents of your object, specially when dealing with value types.

Some people might say that knowledge of memory architecture is irrelevant for application level developers, and I agree partially. Knowing how to save a few bits here and there will make no visible difference on newer iPhones, and premature optimization is a highly shunned practice.

However, both reference and value types can severely slow down your app when misused, and such knowledge will define whether or not you can fix the problem efficiently.

I recently made a pull request to Swift, which inspired me to speak at Campinas's (Brazil) CocoaHeads about how can you do it yourself - and how to leverage the fact that Swift is open source to boost your career. I mixed Jesse Squires's, Mike Choi's and Ole Begemann's articles alongside my own discoveries to create a simple tutorial on how to approach the Swift Community. While the talk is in Brazilian Portuguese, hopefully the contents of the slides are simple enough to guide you through.You can watch it here. (starts at the 39 minute mark)

Understanding how threads operate on the CPU level is the key to writing good concurrent code. This article explains how the CPU executes multithreaded processes, what exactly are iOS's DispatchQueues, what's the point of their "Quality of Services", and why do you have to process UI code in the so called Main Thread.

If you're using TouchID/FaceID as a security measure, chances are you want to protect your user's data in case someone tries to break into his phone. By default, any fingerprint/face is able to validate an user - even if they were added after your app was installed. Learn how to detect system changes in order to stop thieves from accessing your user's data.

In this article, I show how simple is the process of reverse-engineering an App Store's app by using dumped class information and a debugger hooked to a jailbroken device to make Facebook's Messenger allow me to select custom chat bubble colors.