"Modify the following as needed"

[tpict]

I'm following the setup guide, and I'm stuck here

Finally, we will need to write some code to be able to handle FFI in Flutter. Modify the following as needed (replacing library_name and LibraryName with your library name).

Do I need to replace the contents of those files set up by the setup script, or should I keep the createWrapperImpl, createWrapper definitions that are already there?

[fzyzcjy]

https://github.com/fzyzcjy/flutter_rust_bridge/blame/d54eae758f94ca1a5e69787d20f16af39daa89c2/book/src/library/flutter_wrapper.md#L37

cc @GregoryConrad who PRed that helpful part of doc - shall we clarify a bit in the doc?

[GregoryConrad]

Do I need to replace the contents of those files set up by the setup script,

@tpict You were intended to modify the two variable declarations at the top of the setup script so you wouldn't need to manually modify any of those files after.

or should I keep the createWrapperImpl, createWrapper definitions that are already there?

Keep those definitions, but change the LibraryName and library_name parts in the definitions to your library name.

[tpict]

appreciate it! I did modify the variables in the setup script. My question was whether or not I should keep the contents of those files when setting up the Flutter wrapper, or just replace them with what's written out in the guide (swapping LibraryName etc as needed)

[tpict]

I think the answer is to keep the existing content, though it seems that the generated classes aren't respecting the DART_CLASS_NAME variable in the setup script, e.g. if I have

LIBNAME=helloworld # snake_case
DART_CLASS_NAME=HelloWorld # probably is PascalCase version of $LIBNAME

then ffi.dart etc references HelloWorld, which I have to update to Helloworld to successfully build.

When I actually call createLib on my Mac, I get Failed to lookup symbol 'store_dart_post_cobject'. I found the relevant section in the guide but it hasn't resolved the issue for me. What I'm trying to do is: follow the "creating a Dart/Flutter library" section to make a Flutter package I can install in another project, but I want to install it from that package locally using the path: directive in the project's pubspec.yaml so I can test it out. I've copied the .xcframework.zip to the macos dir as directed.

edit again: I also tried moving my project in a Melos monorepo with my Dart/Flutter libraries instead of using the path: directive and I see the same Failed to lookup symbol 'store_dart_post_cobject' issue. Searching the repo I see a lot of solutions around tweaking Runner.xcodeproj, but that's not present if you follow the Dart/Flutter library guide

[tpict]

Still trying to work around this. Are there any "absolute beginners" docs on how DynamicLibrary.executable() works? I can see where store_dart_post_cobject is declared–I just don't understand why dart:ffi isn't finding it.

[GregoryConrad]

Sorry, this escaped me.

Iirc by default the library docs use static linking on iOS/macOS and dynamic loading elsewhere. Thus, the slightly misnamed DynamicLibrary.executable() actually returns the exec file itself, which should have the requested ffi objects if static linking with the rust library was performed.

I’m 99% sure it’s just because it’s not getting linked in. Not sure why, but that’s likely it. Maybe tree shaking or something funky like that?

If this isn’t time sensitive, it might be worth waiting for native assets. If you need this on the sooner end though, then native assets won’t help.

[tpict]

It sounds like native assets would make things easier. But it would be nice to be able to get started on the Rust side in the meantime 🙂

I checked libhello_world.a and it does contain the expected symbol:

0000000000000280 T _store_dart_post_cobject

so I think it's been statically linked correctly? (I'm not a C wiz)

[GregoryConrad]

You don’t want to check the .a; that’ll have the symbols if the rust compiler does its job.

what you’d want to check is the executable of the application itself (the one hidden with the .app bundle). However, I can tell you already that it doesn’t have the symbols (unless the Dart language ffi implementation is wrong, but I highly doubt that). For some reason, the .a is not getting statically linked into the executable. As for why, that’s a bit harder to answer. It’s either not getting found from the podspec or it’s getting tree shaken.

Could you try to see if the example app under flutter_mimir/example here works for you? https://github.com/GregoryConrad/mimir

Melos bs, Melos run build:apple, copy the framework zip over to frameworks folder with the right name, and then finally flutter run in that flutter mimir example

(Sorry for terrible formatting—on phone)

[tpict]

I get a lot of complaints of

ld: warning: object file (/Users/tpict/Projects/mimir/packages/flutter_mimir/example/build/macos/B
uild/Products/Debug/XCFrameworkIntermediates/flutter_mimir/libembedded_milli.a(debug.o)) was built
 for newer macOS version (12.0) than being linked (10.14)

but the app works!

...and it finally clicked: I missed the section on the site about unit testing. I just moved the test in my hello_world app to be an integration test and now it passes. My bad. Thanks so much for all your help 🙏

[GregoryConrad]

Ahh alright! If the integration test on macOS/iOS passes, then it definitely should be statically linking correctly, since integration tests use the full build process. Glad to hear it is working!