hydra-typegen v0.0.2
Hydra Typegen
Motivation
Hydra Typegen is a code generation tool for creating Typescript types for substrate events and extrinsics. Its primary use-case is to provide type-safe interfaces for Hydra mappings. For example, once a typescript class for the Balances.Transfer
event is generated, a mapping can look like
export async function balancesTransfer(
db: DatabaseManager,
_event: SubstrateEvent
) {
const event = new Balances.TransferEvent(_event);
const transfer = new Transfer()
transfer.from = Buffer.from(event.data.accountIds[0].toHex())
transfer.to = Buffer.from(event.data.accountIds[1].toHex())
transfer.value = event.data.balance.toBn()
transfer.block = event.ctx.blockNumber
transfer.comment = `Transferred ${transfer.value} from ${transfer.from} to ${transfer.to}`
console.log(`Saving ${JSON.stringify(transfer, null, 2)}`)
await db.save<Transfer>(transfer)
}
A full sample Hydra project can be found here
Usage
For usage and a list of supported flags, type
hydra-typegen typegen --help
A minimal example for generating classes for the Balances.Transfer
and Treasury.Deposit
events in Kusama:
hydra-typegen --metadata wss://kusama-rpc.polkadot.io Balances.Transfer,Treasury.Deposit
Custom types
Hydra Typegen supports custom substrate types via the --typedefs
flag. The provided .json
file should include type definitions
for the arguments and parameters of the events and extrinsics to be generated. The type definitions file is copied to the generated sources.