substrate-api-client

substrate-api-client a library written in Rust for connecting to the substrate's RPC interface via WebSockets allowing to

• Compose extrinsics, send them and subscribe to updates (synchronously).
• supports composing extrinsics for no_std builds
• Watch events and execute code upon events.
• Parse and print the node metadata.

Prerequisites

In order to build the substrate-api-client and the examples, Rust and the wasm target are needed. For Linux:

curl https://sh.rustup.rs -sSf | sh

rustup default nightly
rustup target add wasm32-unknown-unknown --toolchain nightly

For more information, please refer to the substrate repository.

Substrate node

To execute the examples, a running substrate node is needed. A slightly extended node-template can be found at https://github.com/scs/substrate-api-client-test-node

To build the test node, execute the following steps:

git clone https://github.com/scs/substrate-api-client-test-node
cd substrate-api-client-test-node/
cargo build --release

Run the node:

./target/release/node-template --dev

Tutorial

There is a detailed tutorial in the tutorials folder.

Examples

To run an example, clone the substrate-api-client repository and run the desired example directly with the cargo command:

    git clone https://github.com/scs/substrate-api-client.git
    cd substrate-api-client
    cargo run --example example_get_storage

Set the output verbosity by prepending RUST_LOG=info or RUST_LOG=debug.

The following examples can be found in the examples folder:

• example_compose_extrinsic_offline: Compose an extrinsic without interacting with the node.
• example_contract: Handle ink! contracts (put, create, and call). DEPRECATED!
• example_custom_storage_struct: Fetch and decode custom structs from the runtime. DEPRECATED!
• example_event_callback: Subscribe and react on events.
• example_generic_extrinsic: Compose an extrinsic for any call in any module by supplying the module and call name as strings.
• example_get_storage: Read storage values.
• example_print_metadata: Print the metadata of the node in a readable way.
• example_transfer: Transfer tokens by using a wrapper of compose_extrinsic

Alternatives

Parity offers a Rust client with similar functionality: https://github.com/paritytech/substrate-subxt

Acknowledgements

The development of substrate-api-client is financed by web3 foundation's grant programme.

We also thank the teams at

• Parity Technologies for building substrate and supporting us during development.