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Generic Message Passing (GMP)

Transferring a message between EVM chains​

Generic messages can be transferred between EVM chains, using the Sygma SDK.

To facilitate the transfer, the following steps are required:

  1. Create an instance of the EVMGenericMessageTransfer object and initialize it.
  2. Determine the fee for the transfer, using the EVMGenericMessageTransfer.getFee() method
  3. Prepare, sign, and send the Transfer transaction to the Source network node

The executeDeposit function prepares and populates a deposit transaction. The key parameter is depositData, which is a string requiring a specific format. Refer to the Generic Message Passing documentation for instructions on how to format the depositData string correctly.

There are a few requirements for the Destination chain contract function that gets called. Refer to the Generic Message Passing documentation for details.

1. Initialize the EvmAssetTransfer object​

To initialize the generic message transfer object, the following parameters need to be supplied:

  • An instance of Ethers provider
  • The environment in which the bridge should function
const genericMessageTransfer = new EVMGenericMessageTransfer();

const provider = new JsonRpcProvider("https://URL-TO-YOUR-RPC")

await gmpTransfer.init(
  provider,
  Environment.TESTNET
);

2. Get fee​

To facilitate the transfer of a generic message, a fee must be paid. This fee can be determined by utilizing the genericMessageTransfer.GetFee(transfer) method. You will need to know the destination ChainID as well as the ResourceID that has been configured on the bridge. These details can be determined by inspecting the configurations of the bridge (see here)

const wallet = new Wallet(
  "YOUR PRIVATE KEY",
  provider
);

const transfer = gmpTransfer.createGenericMessageTransfer(
  await wallet.getAddress(),
  DESTINATION_CHAINID,
  RESOURCE_ID,
  DESTINATION_CONTRACT_ADDRESS,
  DESTINATION_FUNCTION_SIGNATURE,
  EXECUTION_DATA,
  MAX_FEE
)

const fee = await assetTransfer.getFee(transfer);

3. Prepare, sign, and send the Transfer transaction to the Source network node​

const transferTransaction = await assetTransfer.buildTransferTransaction(
  transfer,
  fee,
);

// Send the transaction using the wallet
const transferTxResponse = await wallet.sendTransaction(
  transferTx as providers.TransactionRequest,
);

A full example of the above can be found here