Smart Contract Execution

TxTypeSmartContractExecution executes a smart contract with the given data. TxTypeSmartContractExecution is accepted only if "to" is a smart contract account.

Import the ethers and @kaiachain/ethers-ext modules to add kaia features on ethers.js.

Define sender and fee payer addresses and private keys

Set up the provider with the specified kairos testnet URL. A provider in ethers is a read-only abstraction to access the blockchain data.

Also, you can change the provider URL from kairos to quicknode

Create a sender's wallet using the sender's private key and the provider

Create a fee payer's wallet using the sender's private key and the provider

Set the contract address you want to execute into the to field and set ABI

Create a contract instance with ethers.Contract, fill in params contractAddr, abi, provider. You can read and write the contract through this instance

Encode the function name and parameter with the encodeFunctionData function

Build the transaction object with type FeeDelegatedSmartContractExecution

Populate the transaction with necessary details

Sign the transaction by the sender's wallet

Send the transaction to blockchain using fee payer's wallet. Function sendTransactionAsFeePayer adds a signature with FeePayer’s private key to the sender’s signature and transmits it to the blockchain network.

The wait function returns the tx receipt if the tx was sent to the blockchain successfully.

FeeDelegatedSmartContractExecution.js

const ethers = require("ethers");

const { Wallet, TxType } = require("@kaiachain/ethers-ext/v5");

const senderAddr = "0xa2a8854b1802d8cd5de631e690817c253d6a9153";

const senderPriv = "0x0e4ca6d38096ad99324de0dde108587e5d7c600165ae4cd6c2462c597458c2b8";

const feePayerAddr = "0xcb0eb737dfda52756495a5e08a9b37aab3b271da";

const feePayerPriv = "0x9435261ed483b6efa3886d6ad9f64c12078a0e28d8d80715c773e16fc000cff4";

const provider = new ethers.providers.JsonRpcProvider("https://public-en-kairos.node.kaia.io");

const senderWallet = new Wallet(senderPriv, provider);

const feePayerWallet = new Wallet(feePayerPriv, provider);

const contractAddr = "0x95Be48607498109030592C08aDC9577c7C2dD505";

const abi = ["function setNumber(uint256 newNumber)"];

async function main() {

const contract = new ethers.Contract(contractAddr, abi, provider);

const data = contract.interface.encodeFunctionData("setNumber", ["0x123"]);

const tx = {

type: TxType.FeeDelegatedSmartContractExecution,

from: senderAddr,

to: contractAddr,

value: 0,

data: data,

};

// Sign transaction by sender

const populatedTx = await senderWallet.populateTransaction(tx);

const senderTxHashRLP = await senderWallet.signTransaction(populatedTx);

console.log("senderTxHashRLP", senderTxHashRLP);

// Sign and send transaction by fee payer

const sentTx = await feePayerWallet.sendTransactionAsFeePayer(senderTxHashRLP);

console.log("sentTx", sentTx.hash);

const receipt = await sentTx.wait();

console.log("receipt", receipt);

}

main();

output

❯ node FeeDelegatedSmartContractExecution.js

senderTxHashRLP 0x31f8a68203ad850ba43b7400830116379495be48607498109030592c08adc9577c7c2dd5058094a2a8854b1802d8cd5de631e690817c253d6a9153a43fb5c1cb0000000000000000000000000000000000000000000000000000000000000123f847f8458207f6a0f23531b148298b6b686af71c9722702732bed89202dd2a22adf9880b716ed205a074c31ec53da203c1421ae71e36e3b720f9550a00771784562b68c1cfa23e19e8

sentTx 0x8ddf463d1e2d5745b9ba71abce52eb02b6680d9699298c463c72180a7dd2c539

receipt {

to: '0x95Be48607498109030592C08aDC9577c7C2dD505',

from: '0xA2a8854b1802D8Cd5De631E690817c253d6a9153',

contractAddress: null,

transactionIndex: 4,

gasUsed: BigNumber { _hex: '0x9659', _isBigNumber: true },

logsBloom: '0x00000000000040000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000000000000001200000002',

blockHash: '0xa466ec90d778b7ea3e2c2cd3ec2a707fcf31a8c5f44d29d1e85f4c690af8ddb4',

transactionHash: '0x8ddf463d1e2d5745b9ba71abce52eb02b6680d9699298c463c72180a7dd2c539',

logs: [

{

transactionIndex: 4,

blockNumber: 148732388,

transactionHash: '0x8ddf463d1e2d5745b9ba71abce52eb02b6680d9699298c463c72180a7dd2c539',

address: '0x95Be48607498109030592C08aDC9577c7C2dD505',

topics: [Array],

data: '0x0000000000000000000000000000000000000000000000000000000000000123',

logIndex: 14,

blockHash: '0xa466ec90d778b7ea3e2c2cd3ec2a707fcf31a8c5f44d29d1e85f4c690af8ddb4'

}

],

blockNumber: 148732388,

confirmations: 3,

cumulativeGasUsed: BigNumber { _hex: '0x0b61a0', _isBigNumber: true },

effectiveGasPrice: BigNumber { _hex: '0x05d21dba00', _isBigNumber: true },

status: 1,

type: 0,

byzantium: true

}