I second this. Apple's official documentation, while suffering from a decrease in quality over the last decade, is still as good as any "tutorial" you'll find.
I find that you have to find the right bit of documentation, which is not always easy on Apple's site. I often find API documentation that doesn't have enough info to just start using it (it's great for reference, though). You need to find the long-form descriptive documentation they have, which isn't always found by your favorite search engine. (And Apple keeps rearranging their documentation meaning that once you have found it, if you don't bookmark it, finding it again can be nearly impossible.)