[ibiza]

Apple's original Objective-C docs are available at their Documentation Archive. They are quite good.

• Programming With Objective-C (current): https://developer.apple.com/library/archive/documentation/Co...

• The Objective-C Programming Language (older): https://developer.apple.com/library/archive/documentation/Co...

[woadwarrior01]

Also, the Objective-C Runtime reference[1]. About a decade ago, I learnt Objective-C in a day, by reading "The Objective-C Programming Language" and the Runtime Reference. It's such a beautiful and simple language, if you know C. I wish Swift were as simple and succinct. AFAIK, Objective-C++ is still the easiest way to bridge C++ code with Swift code. Knowledge of Objective-C is still relevant for anyone building apps that need to use C++ libraries.

[1] https://developer.apple.com/documentation/objectivec/objecti...

[hugi]

Objective-C was my first "real" language, started working with it with almost no knowledge of C to make some Mac Apps on Rhapsody and later Mac OS X. Nice documentation and an awesome first language, not least due to the lovely Foundation and AppKit frameworks and the nice UIs of ProjectBuilder and InterfaceBuilder at the time. It was pure fun writing software in that environment.

[ethansinjin]

As of Swift 5.9, using Obj-C++ is no longer necessary! https://swift.org/documentation/cxx-interop/

[pjmlp]

Actually the older version from Apple was NeXT's original manual, which isn't on those links, rebraded for Apple.

It was almost page for page identical, minus branding.

Sadly those PDFs are no longer available for download.