Write

You can make a "transaction" interacting with a Smart Contract when you **need to update some state ** in the contract.

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

Define sender address and private key

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 wallet from sender private key and web3 provider

Set the Abi generated from solidity code

Define contract address to interact with

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

Get the number value before updated by using method counter.number()

Create a transaction data to update the number value

The wait function returns the tx receipt if it is completed in the blockchain.

Get the updated value number by using method counter.number()

smartContractWrite.js


const ethers = require("ethers");
const { Wallet } = require("@kaiachain/ethers-ext/v6");
const senderAddr = "0x24e8efd18d65bcb6b3ba15a4698c0b0d69d13ff7";
const senderPriv = "0x4a72b3d09c3d5e28e8652e0111f9c4ce252e8299aad95bb219a38eb0a3f4da49";
const provider = new ethers.JsonRpcProvider("https://public-en-kairos.node.kaia.io");
const wallet = new Wallet(senderPriv, provider);
/* compiled in remix.ethereum.org (compiler: 0.8.18, optimizer: false)
// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.13;
contract Counter {
    uint256 public number;
    event SetNumber(uint256 number);
    constructor(uint256 initNumber) {
        number = initNumber;
    }
    function setNumber(uint256 newNumber) public {
        number = newNumber;
        emit SetNumber(number);
    }
    function increment() public {
        number++;
        emit SetNumber(number);
    }
}
*/
const abi = '[{"inputs":[{"internalType":"uint256","name":"initNumber","type":"uint256"}],"stateMutability":"nonpayable","type":"constructor"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"uint256","name":"number","type":"uint256"}],"name":"SetNumber","type":"event"},{"inputs":[],"name":"increment","outputs":[],"stateMutability":"nonpayable","type":"function"},{"inputs":[],"name":"number","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"uint256","name":"newNumber","type":"uint256"}],"name":"setNumber","outputs":[],"stateMutability":"nonpayable","type":"function"}]';
const contractAddr = "0x95Be48607498109030592C08aDC9577c7C2dD505";
async function main() {
  const counter = new ethers.Contract(contractAddr, abi, wallet);
  console.log("number before", (await counter.number()).toString());
  const sentTx = await counter.increment();
  const receipt = await sentTx.wait();
  console.log("receipt", receipt);
  console.log("number after", (await counter.number()).toString());
}
main();

output


❯ node smartContractWrite.js
number before 291
receipt {
  to: '0x95Be48607498109030592C08aDC9577c7C2dD505',
  from: '0x24e8eFD18D65bCb6b3Ba15a4698c0b0d69d13fF7',
  contractAddress: null,
  transactionIndex: 0,
  gasUsed: BigNumber { _hex: '0x6d6e', _isBigNumber: true },
  logsBloom: '0x00000000000040000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000000000000001200000002',
  blockHash: '0xbc6486ec825cf2388917f6c5c250af3f811bc838ea3f83382c1786d31b1eaaac',
  transactionHash: '0x07c87084001218f66e260cb63c207c676eae3bb4a338b7384457f6a4fdebd5da',
  logs: [
    {
      transactionIndex: 0,
      blockNumber: 148740640,
      transactionHash: '0x07c87084001218f66e260cb63c207c676eae3bb4a338b7384457f6a4fdebd5da',
      address: '0x95Be48607498109030592C08aDC9577c7C2dD505',
      topics: [Array],
      data: '0x0000000000000000000000000000000000000000000000000000000000000124',
      logIndex: 0,
      blockHash: '0xbc6486ec825cf2388917f6c5c250af3f811bc838ea3f83382c1786d31b1eaaac'
    }
  ],
  blockNumber: 148740640,
  confirmations: 1,
  cumulativeGasUsed: BigNumber { _hex: '0x6d6e', _isBigNumber: true },
  effectiveGasPrice: BigNumber { _hex: '0x05d21dba00', _isBigNumber: true },
  status: 1,
  type: 2,
  byzantium: true,
  events: [
    {
      transactionIndex: 0,
      blockNumber: 148740640,
      transactionHash: '0x07c87084001218f66e260cb63c207c676eae3bb4a338b7384457f6a4fdebd5da',
      address: '0x95Be48607498109030592C08aDC9577c7C2dD505',
      topics: [Array],
      data: '0x0000000000000000000000000000000000000000000000000000000000000124',
      logIndex: 0,
      blockHash: '0xbc6486ec825cf2388917f6c5c250af3f811bc838ea3f83382c1786d31b1eaaac',
      args: [Array],
      decode: [Function (anonymous)],
      event: 'SetNumber',
      eventSignature: 'SetNumber(uint256)',
      removeListener: [Function (anonymous)],
      getBlock: [Function (anonymous)],
      getTransaction: [Function (anonymous)],
      getTransactionReceipt: [Function (anonymous)]
    }
  ]
}
number after 292