I am working on the dart_ping package and although it currently is tagged with iOS support, it does not actually support iOS. This is due to the way pub.dev detects supported platforms. I have filed an issue on dart-sdk repo.
Nonetheless, I would like to add iOS support while still preserving support for dart native. Right now, dart_ping works by calling the host OS's ping binary. The ping binary is available on Windows, macOS, Linux, and Android but not on iOS.
Current methods of performing a ping on iOS use native Objective-C code and call them via either method channels or ffi. Since method channels are a flutter feature rather than a dart feature, using them would require dart_ping to depend on the flutter sdk, which would prevent it from being used in a dart native application (perhaps server side).
Ffi on the other hand, is a dart native feature and is capable of doing what I want. However, I cannot seem to find a way to include the iOS framework/library/binary for ping in my dart_ping package in a way that instructs a flutter application to include it and link it to the iOS target/runner.
Is there any way to keep dart native support in my package while also supporting the edge case of iOS needing an extra non-dart framework? Even federated plugins depend on the flutter sdk. It seems to me that we need a pure dart equivalent to the federated plugin system.
TLDR: How do I add a pre-compiled iOS framework or binary to a dart package without depending on the flutter sdk and call it only when the package is used on iOS ?
For your specific case of adding iOS support only for Flutter users of your package but keeping the package as pure Dart without a dependency on the Flutter SDK should be possible by having a Flutter plugin package that depends on your Dart package.
In the pure Dart package you can have FFI calls to a native iOS library, but its actually the Flutter plugin package that supplies the native iOS library per the Flutter documentation for using FFI.
You would of course need to make it very clear in the documentation for your pure Dart package that for iOS, it should only be used via the "wrapper" plugin package.
Unfortunately this is a rather convoluted way to do it, but I don't know of a better way to achieve this as of now.
There is further discussion on this topic in the comments in this issue, which as of today is still open.