If a library vendor provides good docs on their website, that’s just as good as man pages, but in my experience they usually don’t.

There is a staggering amount of misinformation or non-existent information on Stack Overflow. For one simple example: try to figure out how to use the GPS on iPhone. It’s simply impossible. 99% of people on SO think “GPS” is synonymous with “Location APIs” in general. Of the 1% of people who understand the several different data sources used by CoreLocation, nobody can tell you which accuracy settings will cause it to use GPS specifically. If you bother asking, you’ll get a bunch of “middle-brow dismissals” asking why you want to know such a thing, telling you to just use whatever accuracy setting you semantically need, smugly claiming you’re guilty of posing an A-B question, and so on. This is the type of dead simple basic information I would have expected to be present in Apple’s documentation, instead of having to crowdsource it from internet trolls.