Seeking feedback: Polkabind (Swift/Kotlin bindings over Subxt with UniFFI)

[wassimans]

Hi all,

I’ve been working on Polkabind, a thin Rust façade over Subxt that exposes a stable FFI API via UniFFI. The goal is to provide in a first time native Swift and Kotlin bindings (distributed via SwiftPM and Maven) so that iOS and Android developers can interact with Substrate/Polkadot chains without needing to touch Rust directly. Other language support will come after (Python notably).

Concretely:

• Rust façade handles Subxt client, calls, subscriptions, error mapping.
• UniFFI generates bindings → XCFramework + SwiftPM package, and AAR + Maven package.
• Example apps in SwiftUI/Jetpack Compose already demonstrate a transfer flow against a Chopsticks node.
• Roadmap includes balances, fees, staking, multisig, subscriptions, etc.

I recently applied to the W3F Open Source Grant program. One reviewer asked whether this project would truly be useful to the ecosystem, and I’d like to get your perspective as Subxt’s maintainers:

• Do you see a project like Polkabind as aligned with Subxt’s goals of being bindable to other languages (cf. this discussion)?
• Would providing high-level Swift/Kotlin APIs over Subxt lower the barrier for mobile/Web3 developers to integrate with Polkadot/Substrate chains?
• Is there anything in Subxt’s roadmap that might overlap or conflict with this approach?

I’m not asking for endorsement of funding, only for your technical perspective: whether this project makes sense in your view and how it might fit into the Subxt ecosystem.

Thanks a lot for your time, and for your work on Subxt, it’s been very inspiring to contribute (I added the FFI example via C) and I’d love to make Polkabind a useful companion for the ecosystem.

Best,
Wassim

(CC @jsdw)