The library provides tools and primitives to simplify the development of chain extensions for ink! and Substrate.

OBCE automatically generates everything needed to correctly call chain extension from ink! smart contracts, and to correctly implement the chain extension itself on the Substrate side.

OBCE' macros automatically generate all the logic related to argument encoding/decoding, function and extension identifier calculation and error handling.

The ink! side of OBCE is fully automated, while with Substrate all that's left is to implement the chain extension using generated traits.

In this tutorial we'll spin up our own Substrate node with rand-extension enabled.

1. Clone substrate-contracts-node repository.
2. Copy examples/rand-extension/chain-extension folder to a cloned substrate-contracts-node repo and add it as a workspace member to Cargo.toml:

# ...

members = [
    'chain-extension',
    'node',
    'runtime'
]

# ...

3. Add rand-extension to runtime/Cargo.toml:

rand-extension = { path = "../chain-extension", default-features = false, features = ["substrate"] }

Also, add rand-extension/substrate-std to feature list that is activated when std feature is active:

[features]
# ...

std = [
    # ...
    "rand-extension/substrate-std",
]

4. Launch node with ./target/debug/substrate-contracts-node --dev --tmp.
5. Install cargo-contract using the installation guide.
6. Create new contract via cargo contract new command.
7. Replace lib.rs file with the one, that is provided in examples/rand-extension.
8. Modify contract's Cargo.toml to include chain extension as a dependency, and to activate ink-std feature if std feature of a contract is enabled. Replace PATH_TO_CHAIN_EXTENSION_CRATE with the path to rand-extension crate:

[dependencies]
# ...

rand-extension = { path = "PATH_TO_CHAIN_EXTENSION_CRATE", default-features = false, features = ["ink"] }

[dev-dependencies]
# Include OBCE as a dev dependency to test the contract
obce = { git = "https://github.com/727-Ventures/obce", default-features = false, features = ["ink-std"] }

[features]
# ...

std = [
    # ...
    "rand-extension/ink-std"
]

9. Build contract using cargo contract build.
10. Deploy contract using cargo contract or Contracts UI.

• examples directory
• pallet-assets