Objective-C Internals

https://alwaysprocessing.blog/series/objc-internals

by ingve • 3 years ago

96 85 3 years ago

atorodius• 3 years ago

I learned to program in Objective C, it was fun. Spent many hours digging behind the scenes, but the only fun fact I remember is that it’s a strict superset of C, so any C program is a valid Objective C program. Always found this fascinating.

Are people still using it today? I thought Swift took over.

TazeTSchnitzel• 3 years ago

Can't speak to personal experience, but my understanding is Objective-C++ (which is most of C++ plus all of Objective-C) is still popular for bridging the Objective-C/Swift and C++ worlds. Though apparently Swift is getting a C++ interop system, so that might become less common!

lapcat10• 3 years ago

Are people still using it today?

Yes, I am. Apple is too:

https://blog.timac.org/2022/1005-state-of-swift-and-swiftui-...

In my estimation, these are the primary reasons why some developers continue to use Objective-C:

1) Rewriting an existing code base is almost always massively expensive and dangerous.

2) 9 years later, the Swift tooling is still atrocious. Compile times are much longer, the compiler still crashes, the debugger still doesn't work reliably. It's a major step down from the mature Objective-C tooling.

3) There are still land mines with interoperability between Swift code and Apple's underlying Objective-C frameworks. Performance bottlenecks, unexpected object bridging issues, erroneous nullability annotations, etc.

4) C and C++ compatibility, as mentioned by another commenter.

MichaelZuo3• 3 years ago

Since Apple now controls the entire hardware stack for all their products (except the mac pro), they could conceivably design their own assembly language ('Apple Assembly'?) optimized for, and only for, Apple silicon and bypass the problem.

jamil7• 3 years ago

9 years later, the Swift tooling is still atrocious. Compile times are much longer

To be fair you can’t really compare them since the Swift compiler is giving you a lot more guarantees than Objective-C which gives you basically zero. Rust is also atrociously slow to compile.

catiopatio5• 3 years ago

Almost no new projects within Apple are written using Objective-C, and old code is actively rewritten for many reasons, with security being a large one.

zffr• 3 years ago

Most new code is probably written in Swift, but there’s still lots of ObjC code out there and people are still writing it to maintain/extend those code bases.

flohofwoe• 3 years ago

I use ObjC as a thin layer to talk to macOS/iOS frameworks with the rest of the code being mostly C and some C++. Swift would not only be complete overkill for that but also a lot more hassle with build system integration (don't even know if cmake supports mixed C/C++/Swift projects out of the box)

dagmx5• 3 years ago

FWIW , Cmake does support mixed language projects with Swift.

miramba• 3 years ago

I do. Not only because I don‘t want to rewrite my apps but because for me Objective-C is beautiful and better to read than any other language I tried. I never saw the point of learning a new language to implement the same things. The only benefit I could see was for Apple, pushing me a bit farther into their ecosystem which is incompatible with anything else. When it became obvious that Swift was the way to go I switched to js / hybrid app development for new projects. This seems to also die out now, but I‘m still sticking to it.

mrbombastic• 3 years ago

The bridging layer for react native apps is written in Objective-C for most native iOS things, so most react native libraries and apps will have a fair amount. Older apps and Apple also ensure it will stay alive for some time to come.

vbezhenar2• 3 years ago

I prefer Objective C to Swift. I'm not professional Apple developer, though, just write code for fun in my spare time, so I have luxury of being able to select tools I like. I guess, in professional setting Swift took over most new projects.

tagyro• 3 years ago

I wrote my latest (released) iOS app in obj-c.

While I see some of the benefits of swift, I find it unnecessarily unreadable. One might argue about this, but as a developer, I value how readable the code is (no matter the language).

Going over various projects written in swift on github, more than 50% don't even compile without serious refactoring.

OTOH, grab a project in obj-c, from 15+ years ago, compiles with minimal changes (or, most of the time, without any).

I'm a big fan of Chris Lattner and his work, but swift is not his most successful children. While I believe his intentions were good, the end result is a mess worse than brainfuck (the programming language).

YMMV

pjmlp11• 3 years ago

Metal is written in Objective-C, with Swift bindings.

BrianHenryIE2• 3 years ago

Also worth a look are:

https://github.com/iosre/iOSAppReverseEngineering

https://www.amazon.com/NSHipster-Obscure-Topics-Cocoa-Object...

and the ultimate:

https://www.mikeash.com/book.html

instagary• 3 years ago

Have you come across any newer mobile RE resources?

lauriewired• 3 years ago

(This is my own channel), but I recently made a video on Objective C calling conventions specifically for Reverse Engineers that you might enjoy, with more iOS videos incoming:

https://youtu.be/eI-Btfjp-fg

As for modern RE resources, I can recommend Jonathan Levin's series of books on MacOS and iOS internals as a good reference. It's probably the newest information you are going to be able to get on iOS/mac internals outside of apple.

https://newosxbook.com/

BrianHenryIE2• 3 years ago

Nothing comes to mind that’s similar to that first link. I’m really just replying to emphasize to others how great it is. I learned a ton from it.

1propionyl• 3 years ago

+1 for Mike Ash's Friday Q&A. Very fond memories of seeing a new post show up in my feed.

grishka• 3 years ago

As someone who's trying to bridge macOS's native APIs with Java for a future project, this is useful for me.

tambourine_man4• 3 years ago

Believe it or not (i'm walking on air), there was a time when Apple had an official Cocoa-Java bridge . They were betting heavily on it, rewrote WebObjects on Java, etc.

Then, for some reason, people began to realize ObjC was quite all right after all, despite its crazy bolted-on syntax, and it “caught on”, for some reason. Maybe because Mac OS X was already dog slow and memory hungry as it was to even consider Java. And, funnily enough, ObjC was the slower solution to C/C++ on Carbon, that they somehow menage to run on a phone with 128MB of RAM and a DVD player SOC.

r618• 3 years ago

just CD player initially

first iOSs didn't support user's videos playback

pjmlp11• 3 years ago

Yeah, the Mac OS community was raised in Object Pascal and C++, Java came to be due to a mix of its initial hype, agreement with Sun, and fear that Objective-C would be too alien for the Mac developer community, due to its syntax and semantics.

Copland was going to be a microkernel based with C++ frameworks, as an additional note, similar in spirit on how BeOS turned out to be.

As that proven not to be an issue, and the community did indeed adopt it, they decided to cut down on costs of having multiple languages.

A bit ironic, as we are back to the Object Pascal / C++ days, with two similar inspired languages.

fiddlerwoaroof• 3 years ago

I wrote a bridge between macOS APIs and Common Lisp using the Objective-C runtime and it’s pretty nice to be able to work with system APIs at a high level, and not be forced down to “bag of bytes” C FFI. Hopefully, Apple’s move towards Swift will maintain the Objective-C runtime even if they eventually deprecate the language itself.

ibiza• 3 years ago

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• 3 years ago

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...

ethansinjin• 3 years ago

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

hugi• 3 years ago

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.

pjmlp11• 3 years ago

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.

fabiensanglard• 3 years ago

What a beautiful website! Sadly cannot find a RSS feed :/ !

lapcat10• 3 years ago

https://alwaysprocessing.blog/feed.xml

iamflimflam1• 3 years ago

I really enjoyed Objective-C some very powerful ideas around message sending and handling. And you could just use C and C++ I loved it. I never got to use smalltalk. And Objective-C felt as close as I could ever get.

Objective-C Internals

Related Stories