Maintainability and readability in swift

My notes on writing maintainable and readable swift code


Although you’ll get slightly faster build time by merging all extensions into one class, at the same time you sacrifice code readability and ease of maintenance.

Instance vs value

Using instance variables will increase your compilation time. In the end,

Focus on comprehension from a cognitive perspective

Scrolling is bad for the brain -> “cheetah-theory” -> BRAINS ARE GREATE WITH spatial thinking. scanning is cognitively expensive. Less info creates focus. And you don’t have to look at unrelated data that you have to actively filter out. Build time won’t suffer much from many files. Hierarchies are easy to reason about because your slice of what you are working on is unfolded, and your never working on everything at once.


Scrolling long pages of code is bad for your brain. The human brain has strong spatial recognition and if things are compartmentalised into separate “rooms” then the brain will use less bandwidth.


  • More on using extension to organize code:
  • Natasha the robot also has a book that has a chapter or two with organizing code with extensions