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 web3 and @kaiachain/web3js-ext packages to add kaia features on web3

Define sender, fee payer addresses and private keys

Define contract address and abi

Set up the provider with the specified kairos testnet URL. A provider in web3 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 with the private key using web3.eth.accounts.privateKeyToAccount

Create a fee payer's wallet with the private key using web3.eth.accounts.privateKeyToAccount

Define contractAddr and contractAbi, you can get the contract address and Abi from compiled solidity code or blockchain explorer

Create a contract instance using Web3.eth.Contract with defined contractAbi and address. You can read and write the contract through this instance

Encode the function data for the setNumber function, encodeABI convert the data into bytecode

Create the transaction object to interact with the contract

Set type: TxType.FeeDelegatedSmartContractExecution for transaction to change contract state with a fee payer

Set data: data for earlier encoded function data

Sign the transaction with sender account using signTransaction

Sign the transaction with fee payer account using signTransactionAsFeePayer

Send the transaction to blockchain. It will return the transaction receipt

FeeDelegatedSmartContractExecution.js

const { Web3, TxType } = require("@kaiachain/web3js-ext");

const senderAddr = "0xa2a8854b1802d8cd5de631e690817c253d6a9153";

const senderPriv = "0x0e4ca6d38096ad99324de0dde108587e5d7c600165ae4cd6c2462c597458c2b8";

const feePayerAddr = "0xcb0eb737dfda52756495a5e08a9b37aab3b271da";

const feePayerPriv = "0x9435261ed483b6efa3886d6ad9f64c12078a0e28d8d80715c773e16fc000cff4";

const provider = new Web3.providers.HttpProvider("https://public-en-kairos.node.kaia.io");

const web3 = new Web3(provider);

const senderAccount = web3.eth.accounts.privateKeyToAccount(senderPriv);

const feePayerAccount = web3.eth.accounts.privateKeyToAccount(feePayerPriv);

const contractAddr = "0xD7fA6634bDDe0B2A9d491388e2fdeD0fa25D2067";

const contractAbi = JSON.parse('[{"inputs":[{"internalType":"uint256","name":"newNumber","type":"uint256"}],"name":"setNumber","outputs":[],"stateMutability":"nonpayable","type":"function"}]');

async function main() {

const contract = new web3.eth.Contract(contractAbi, contractAddr);

const data = contract.methods.setNumber(0x123).encodeABI();

const tx = {

type: TxType.FeeDelegatedSmartContractExecution,

from: senderAddr,

to: contractAddr,

data: data,

};

// Sign transaction by sender

const signResult1 = await senderAccount.signTransaction(tx);

console.log("senderTxHashRLP", signResult1.rawTransaction);

// Sign and send transaction by fee payer

const signResult2 = await feePayerAccount.signTransactionAsFeePayer(signResult1.rawTransaction);

console.log("signedTx", signResult2.transactionHash);

const receipt = await web3.eth.sendSignedTransaction(signResult2.rawTransaction);

console.log("receipt", receipt);

}

main();

output

❯ node FeeDelegatedSmartContractExecution.js

senderTxHashRLP 0x31f8a68203b8850ba43b74008301087994d7fa6634bdde0b2a9d491388e2fded0fa25d20678094a2a8854b1802d8cd5de631e690817c253d6a9153a43fb5c1cb0000000000000000000000000000000000000000000000000000000000000123f847f8458207f5a07d40391ae45f7d515becb1aff3b99e7d8b05299b268daa623fb045d981d89c44a0117c23ab37da35ce5206525852ce27f7edc9401e0ee8069a9a396daa64d0c85d

signedTx 0xfa69f712a8d748e294caa1b95df51f8974a0bcf620af6c1b8a7614999a20b447

receipt {

blockHash: '0x4f852e6a2d320287f20cf34c24546f51f53ebdbbc4a4cacee93525e678abf275',

blockNumber: 148744853n,

cumulativeGasUsed: 36990n,

effectiveGasPrice: 25000000000n,

from: '0xa2a8854b1802d8cd5de631e690817c253d6a9153',

gasUsed: 36990n,

logs: [],

logsBloom: '0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000',

status: 1n,

to: '0xd7fa6634bdde0b2a9d491388e2fded0fa25d2067',

transactionHash: '0xfa69f712a8d748e294caa1b95df51f8974a0bcf620af6c1b8a7614999a20b447',

transactionIndex: 0n,

type: 0n

}