Is it possible to write plain C iOS app in 2025?

Objective-C is designed in such a way that, generally speaking, anything you can do with Objective-C syntax can also be done with a simple C function call to one of the Objective-C runtime functions. So you can write an entire iOS app in pure C. However, the Objective-C stuff is a lot more pleasant to use if you use the syntax for it.

As others have mentioned, for something like a simple game (rather than a normal GUI application), SDL offers a convenient wrapper that allows you to avoid touching anything Objective-C-related yourself, so you could write an entire app using only the SDL API, which is pure C. A nice bonus of that approach is that it would then work on other platforms with zero code changes.

Another source of C wrappers is Apple themselves, as iOS has a number of C interfaces like CoreFoundation that reduce how much Objective-C stuff you have to directly interact with, but there's nothing like that for UIKit, and every iOS app has to use UIKit at least a little.

Yes. And many are when you require a common code-base for iOS, Android, and other devices. (But C++ is used more commonly)

Video games are the ones that do this by default. It would be close to impossible to have feature parity by coding a game for iOS in Swift, for Android in Java, for Steam in C++, etc. Unreal or Unity will have C/C++ code-bases with very light integration layers to do system calls.(The payment system may have code in Objective-C, for example, but mostly a wrapper for convenience reasons)

The other extreme is to just use webapps in an electron wrapper. But electron itself is build in C++.

My guess is that most developers are going to use the default Java/Swift combination for mobile development because that is what each company taught in their websites. I would prefer, thou, that engineers were more inclined to use opensource solutions to create common interfaces and avoid vendor lock-in. But cool events and free tutorials are hard to beat.

If you just want to write C and are ok linking to stuff that is in other languages, then I used SDL2 for my game which I wrote in C and is on the app store. It was a very pleasant experience, and if I were doing an iOS thing again, I would likely do something similar.

I think I had one objective C file in there for calling a library function I needed, but otherwise I just wrote C code.

No, not really.

You will notice that everyone that is replying that you can, also mentions that actually you have to make use from the Objective-C runtime from C.

So for all pratical purposes you will be writing an Objective-C application, manually writing the code that the Objective-C compiler used to generate when it was originally designed as a macro pre-processor generating C code at StepStone.

The way iOS is designed the bottom layer for userspace applications is Objective-C, not pure C UNIX style, and using the C APIs from the Objective-C runtime hardly changes that, you will be calling into the Objective-C runtime one way or the other.

Yes, technically it's possible by wrapping the ObjC runtime API, see solutions like these:

- https://github.com/garettbass/oc

- https://github.com/mitchellh/zig-objc

Whether that's better than writing ObjC directly is another question, think of ObjC as a convenient syntax sugar wrapper around macOS/iOS APIs which you only need in those parts of your application that talk directly to operating system APIs.

Also Apple is maintaining a C++ Metal API wrapper now (ok, technically that's not C): https://developer.apple.com/metal/cpp/

If you just want do to simple 'game-y stuff' (3D rendering, audio, low level touch input) you can also check out the Sokol headers (shameless plug): https://github.com/floooh/sokol, or I guess SDL will work too (especially with the new GPU API in SDL3) - at least the sokol header implementation code needs to be compiled as ObjC on macOS/iOS though (e.g. pass `-x objective-c` to Clang), since the macOS/iOS specific code paths are written in ObjC.

For the general case or when you need to access OS frameworks that are not wrapped by 3rd-party libraries:

If your app is mainly C code, have a thin layer of ObjC code that sits on top of the system ObjC APIs and which exposes a C API to the rest of the application.

Don't just tunnel every ObjC call through to C, instead wrap small feature blocks in ObjC and expose those features through a much simplified C API.

E.g. a hybrid C/ObjC application with only the necessary amount of ObjC code for talking to OS APIs, and all the 'business logic' in C (or another language, like C++, Zig or Rust).

Yes, it's basically writing a nibless objective-c application but manually translating all invocations to objc_msgsend yourself. You're not going to be able to avoid the objective-c runtime though.

There is this beautiful single-header library to write simple graphical programs in C, portably to standard unixes, macos, and windows:

https://github.com/ColleagueRiley/RGFW.git

It was discussed recently around here: https://news.ycombinator.com/item?id=42217535

The macos backend is a neat hack, written in pure C.

Yes, Objective C is built on some deep C calls you can call directly. I was a part of a project that built an automatic wrapper generator for C. Check it out at https://felixk15.github.io/posts/c_ocoa/

I think a better question is - could people practically write macos/ios apps without xcode.

I remember the feeling I first got (decades ago) when moving from C to objective C.

Having an xcodeproj was like the camel's nose under the tent, and then you couldn't go back. And you frequently had a big mess going forward when the next xcode version came out and it wouldn't work.

I remember having to set up an Ogre3D (A C++ 3D engine) project so I could compile it with XCode.

For some reason it required a bit of objective C for it to work with opengl.

I sold my macbook about 2 years later, around 2015.

Here is the original StackOverflow question that inspired that GitHub project: https://stackoverflow.com/questions/10289890/how-to-write-io...

One of the other answers also explains how to write a MacOS app using pure C.

I wrote an app that has minimal Objective C that then just calls C++ code. You can either add .cpp files to your project, or if I recall correctly, you can just define C++ functions in your obj c files. In my app, Objective C just sets up the UI and then it calls C++ functions to do calculations. Not exactly your question, but might be helpful.