> Explanations of design intent might be the most underrated kind of documentation. There's so little of that nowadays in general, in any technology. Personally, I blame shortened attention spans, the death of programming books, and the rise of Stack Overflow. I'm not familiar with the Apple ecosystem, is it really worse in this regard than others?

I also blame dogmatic misunderstandings that have crystalized around "Agile." Maybe back in the day a some cookbook process specified a lot of useless documentation be created, but many people seem to have thrown the baby out with the bathwater and declared all documentation useless or not worth the effort.

Also some programming books are to blame. IIRC, the book "Clean Code" completely rejects comments because they can get out of sync with the code and therefore be misleading, and "clean code" should be self-documenting. However, all code can ever tell you is what is, it can never tell you why or what was really intended. Also, when you really think about it, method and variable names are comments too, which can get just as out of sync with what's really going on than a comment block.

To be fair to “Clean Code”, although it’s stance is clearly towards less (superfluous) comments, it recommends using doc strings to document intent.

What it recommends to just delete are comments like

  var speed # the speed

I completely agree. I never understood the argument of docs getting out of sync. If an organization prioritizes documentation then the comments are just as likely to stay in sync as the variables.

In-line documentation getting out of sync is a purely organizational problem. If documentation is valued by the organization inline documentation won't get out of sync.

It's the easiest to keep in sync. It lives in the code it documents. It's in the same version control repo and the same version of the source building a binary can build the docs. If it ever does get out of sync with the code it's the most straightforward to fix because it's the same process for fixing an issue in the code itself.

And presumably you can track down when the inline docs diverged from the implementation, and who did it.

Documentation isn't automatically checked. Tests and sample code are a better alternative, since you can configure things to give you a build error if they ever get outdated.

If you are changing some code that has inline documentation it's your responsibility to update it. If that is not your responsibility then it's an organizational failing. Keeping inline documentation up to date and clean should be part of the organization's coding style guidelines.

Tests are not documentation. They only test a very limited "what" or "how" and give no explanation of "why". If it's closed source software and you're only shipping a binary, the tests do not go with the binaries so they're meaningless to third parties. Sample code isn't much better. Without the organizational pressure to keep it in sync with the code it's demoing and "why" explanations it doesn't provide a lot of useful insight for third parties.

Organizational pressure is a scarce resource, it's a waste to spend it on things that you can do with tooling. Keeping tests and sample code up to date involves more than just fixing compilation errors, sure, but the compilation error gets you reading and paying attention to the right piece of material.

Apple's architectural/design intent documentation is sort of hit or miss. The biggest issue (IMHO) with overall architecture documentation is too often it doesn't make it into written documentation. The key insights are sometimes the middle ten minutes of a WWDC keynote or presentation.

If you didn't attend that WWDC session or pour over all the recordings you've missed that particular key concept. So you're then sort of feeling your way around some new technology and making it work but it's not as efficient or elegant as if you had the whole picture.

Because there's so little documentation time and Apple does not (as a rule) do engineering blogs or similar there's not a lot of of opacity into inner workings or designs. From the outside there's a lot more reading of tea leaves than you see for other platforms.

I see. Engineering blogs do fill some of that role in Microsoft’s stacks. This is not completely ideal either. Blog posts are frozen in time, and newer articles tend to only describe the deltas. So to get a current understanding, you also have to puzzle together various bits and pieces. But at the very least, blogs are easily searchable.

While blog posts aren't ideal they're (like you point out) better than nothing. But blogging goes completely against the grain of how Apple operates internally. The WebKit blog is a singular notable exception because that's a highly visible Open Source project. Even the free-form Q&A portions of WWDC sessions are rarely as frank as they should be in terms of usability.

No blogs is fine, that's just the corporate culture, but no blogs and no good up to date architectural documentation is a huge problem. It leads to cargo-cult understanding or complete misunderstandings by outside developers. Hell, it leads to cargo-cult understanding by internal developers.