What is Reddit's opinion of Programming iOS 14: Dive Deep into Views, View Controllers, and Frameworks?

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You need to build a very good understanding of the technologies you are using; sadly, for iOS, there is a very minimal amount of good resources, since UIKit, Core Animation, Core Graphics and Core Text, the frameworks used for the UI of an app, are really quite complex and simultaneously closed source, so even a lot of people who write tutorials, books and courses have very poor understanding of what they are talking about, so if you want a good example, you could probably start with something more approachable and cross-platformy, like the Foundation framework as an example:

For instance, computers have the notion of files and filesystems. Files are sequences of bytes that can be read from or written to a disk. Go and read how computers do that, how they communicate to the drive, how they load those files into the memory, how they navigate the filesystem, what they try to do to avoid corruption, how compression works etc. etc. You can discover these little topics for yourself one-by-one and try digging into the inner workings of things. Because files are a ubiquitous thing, you'll be able to find a lot of good resources to read about them, I also encourage you to read about the technology using books that are written with a different programming language. Once you find that a resource really makes you understand the workings, it's a good sign. And because Foundation is open-source, you can read the actual code.

Now, the UI is all about colouring (or drawing) pixels into rectangular regions and laying them on top of each other (this is called compositing). A UIView stores some rendering and sizing information (like colours, frames, constraints etc.), and then the system will go and draw the pixels based on these data — and it dos this 60 or even more times a second to produce an illusion of animation . Read about the view hierarchy, the layout and the drawing passes, text layout, interpolation (used when animating), pixel formats, hit-testing, etc. etc — hope you get the idea. Sadly, this is the only book I can recommend on UIKit, since, as I mentioned, most other authors do not understand these things.