Seamless interaction with any Polkadot SDK based chain for Swift, Kotlin, Python and more!
Polkabind is a library that opens the Polkadot ecosystem to programming languages other than Rust. It exposes mainly standard wallet-level functionality (key management, balance queries, extrinsic building, signing, RPC, event subscriptions and more) to other languages (Swift, Kotlin, Python, Javascript and more) by exposing the Subxt library through FFI (foreign language interface).
As of today, the main and supported languages that can be used to interact with a chain built on the Polkadot SDK are:
- Rust: primary and official through Subxt, Polkadot SDK and FRAME.
- Javascript/Typescript: widely used and community supported through tools like: PAPI and PolkadotJS and more.
Some projects tried to expose the same rich functionality for other languages, but many are way behind in terms of API exposure compared to Subxt. And still, it's really difficult to produce safe code in other languages compared to Rust, and especially compared to the established Rust cryptographic libraries used under the hood by Subxt and FRAME.
Subxt itself is the primary Rust/Webassembly based tool used to interact with Polkadot SDK based chains, and many community developer tools use it internally. But for a developer, other than the Rust language learning curve, Subxt adds to it its own learning curve because of it's rich API coverage and the complexity of the blockchain based interactions in general.
Polkabind tries to open the Polkadot ecosystem to other languages in a smart way by:
- creating a façade/abstraction on top of Subxt itself: we use Subxt, we don't replace it. Subxt is our source of truth. The façade exposes mainly standard wallet-level functionality, no fancy interactions, at least for now.
- simplifying the developer experience: instead of crafting a big block of code using Subxt to do a simple transfer, Polkabind abstracts it to be a simple function exposed to other langugaes.
- the façade is translated to other languages through FFI (C ABI), the standard bridge between Rust and most runtimes.
- Polkabind will produce small ready-to-import libraries for major languages: Swift, Kotlin, Nodejs, Python and more. And later, those libraries will be published to each language package manager's repository: for Nodejs, it will be as simple as npm install @polkabind/latest.
- If Subxt gains a new feature, a single Rust change in Polkabind automatically propagates to every supported language.
This is a high level workflow showcasing the production a Swift Polkabind package.
flowchart TD
%% ──────────────────────────────────────────────
%% Repositories (left-to-right data flow)
%% ──────────────────────────────────────────────
subgraph CORE["**polkabind** (Rust + Subxt façade)"]
A[Push / Tag vX.Y.Z]
end
subgraph CORE_CI["Core repo CI ( GitHub Actions )"]
direction LR
B1[Build<br/>⚙️ Rust dylib<br/> device + sim] --> B2[Generate Swift stubs<br/>🔧 UniFFI]
B2 --> B3[Bundle xcframework<br/>+ Package.swift]
B3 -->|git push files & tag| B4[Mirror into<br/>**polkabind-swift-pkg**]
end
subgraph SWIFT_REPO["**polkabind-swift-pkg** (repo)"]
C[New commit<br/>+ tag vX.Y.Z]
end
subgraph SWIFT_CI["Swift repo CI ( GitHub Actions )"]
D1[Zip package] --> D2[Create GitHub Release<br/>📦 polkabind-swift-pkg.zip]
end
subgraph CONSUMER["Developer / CI using SwiftPM"]
E[Swift / iOS App<br/>adds SPM dependency<br/>→ fetches Release]
end
%% ──────────────────────────────────────────────
%% Link everything
%% ──────────────────────────────────────────────
A --> CORE_CI
B4 --> C
C --> SWIFT_CI
D2 --> E
%% ──────────────────────────────────────────────
%% Styling helpers
%% ──────────────────────────────────────────────
classDef repo fill:#f9f9f9,stroke:#bbb;
classDef pipeline fill:#eef3ff,stroke:#87a9ff;
classDef release fill:#e8fce8,stroke:#78c878;
class CORE,SWIFT_REPO repo
class CORE_CI,SWIFT_CI pipeline
class D2 release
For Kotlin/Android, it's roughly the same process, but we publish to Jitpack.io, so it's really easy for any Android app to fetch and use the latest polkabind-kotlin-pkg.
Here's what it looks like to use Polkabind in Swift:
// build the address, compose the dynamic call,
// sign, submit, watch for finality …
let dst = Value::variant(
"Id",
Composite::unnamed(vec![Value::from_bytes(arr)]),
);
let client = OnlineClient::<PolkadotConfig>::from_url(url).await?;
let tx = dynamic_call(
"Balances",
"transfer_allow_death",
vec![dst, Value::u128(amount)],
);
client
.tx()
.sign_and_submit_then_watch_default(&tx, &signer)
.await?
.wait_for_finalized_success()
.await?;// one blocking FFI call – done 🎉
try Polkabind.doTransfer(destHex: destHex, amount: amt)import dev.polkabind.doTransfer
// one blocking FFI call – done 🎉
...
doTransfer(destHex, amt.toULong())Behind the scenes Polkabind executes that same Rust (left column) but exposes a single, ergonomic Swift API.
A ready to launch iOS and Android app, featuring a balance transfer of from Alice's account to Bob's account. You can check the accounts initial balances after launching a local node with Chopsticks (see below).
examples/
└── app
├── Android
│ ├── app
│ │ ├── build
│ │ ├── build.gradle.kts
│ │ ├── proguard-rules.pro
│ │ └── src
│ ├── build.gradle.kts
│ ├── gradle
│ │ ├── libs.versions.toml
│ │ └── wrapper
│ ├── gradle.properties
│ ├── gradlew
│ ├── gradlew.bat
│ ├── local.properties
│ └── settings.gradle.kts
└── iOS
└── PolkabindExample
├── PolkabindExample
├── PolkabindExample.xcodeproj
├── PolkabindExampleTests
└── PolkabindExampleUITests
SwiftUI snippet used in the the Swift example:
Button("Send Transfer") {
status = "⏳ Sending…"
Task.detached {
do {
try Polkabind.doTransfer(
destHex: "0x8eaf…a48",
amount: 1_000_000_000_000
)
status = "✅ Success!"
} catch {
status = "❌ \(error)"
}
}
}Compose UI snippet used in the the Kotlin example:
Button(onClick = {
// kick off a background thread for the blocking FFI call
Thread {
runCatching {
val amt = amountText.toLongOrNull()
?: throw IllegalArgumentException("Bad amount")
doTransfer(destHex, amt.toULong())
}.fold(
onSuccess = { status = "✅ Success!" },
onFailure = { status = "❌ ${it.message}" }
)
}.start()
status = "⏳ Sending…"
}, modifier = Modifier.fillMaxWidth()) {
Text("Send Transfer")
}
- launch an instant-finality Polkadot dev chain using Chopsticks.
npx @acala-network/chopsticks \
--config=https://raw.githubusercontent.com/AcalaNetwork/chopsticks/master/configs/polkadot.yml \
--build-block-mode Instant-
open PolkabindExample.xcodeproj in Xcode.
-
Add the binary package:
- Xcode → Package Dependencies → «https://github.com/Polkabind/polkabind-swift-pkg»
- Select the latest Release (tag vX.Y.Z).
- Link “Polkabind” to your app target (Xcode does this automatically when you tick the checkbox).
-
run on a simulator.
-
tap "Send Transfer":
- In the simulator you’ll see ✅ Success!; in the Chopsticks console the extrinsic is instantly finalised.
That’s all: no Rust toolchain, no Subxt boilerplate, just a tiny binary framework you can ship in any iOS app.
- launch an instant-finality Polkadot dev chain using Chopsticks.
npx @acala-network/chopsticks \
--config=https://raw.githubusercontent.com/AcalaNetwork/chopsticks/master/configs/polkadot.yml \
--build-block-mode Instant- Forward the RPC port into the emulator:
adb reverse tcp:8000 tcp:8000-
open examples/app/Android in Android Studio.
-
Add the binary package:
- In your settings.gradle.kts (project root) make sure you have JitPack:
dependencyResolutionManagement {
repositories {
google()
mavenCentral()
maven { url = uri("https://jitpack.io") }
}
}- In app/build.gradle.kts add:
dependencies {
// … other deps …
implementation("com.github.Polkabind:polkabind-kotlin-pkg:<latest-tag>")
}Make sure to grab the latest Kotlin package release tag and replace the placeholder.
- Allow cleartext traffic, we’re talking plain HTTP, so in your AndroidManifest.xml:
<application
…
android:usesCleartextTraffic="true"
android:networkSecurityConfig="@xml/network_security_config">
…
</application>- And add res/xml/network_security_config.xml:
<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
<base-config cleartextTrafficPermitted="true" />
</network-security-config>-
Hit run on an emulator.
-
tap "Send Transfer":
- In the emulator you’ll see ✅ Success!; in the Chopsticks console the extrinsic is instantly finalised.
That’s all: no Rust toolchain, no Subxt boilerplate, just a single Gradle dependency and a tiny AAR you ship with your APK.
This is a work-in-progress, please visit polkabind.dev for a summary of the expected roadmap.
Polkabind is licensed under the Apache License, Version 2.0 (see LICENSE).
Polkabind uses Subxt, which is dual-licensed under either: • Apache License, Version 2.0, or • GNU General Public License v3.0 (or later)
Polkabind explicitly elects to use Subxt under the terms of the Apache License, Version 2.0.