web3x-codegen

Contract interface code generator for web3x.

Interacting with contracts without type safety is tedious at best, and dangerous at worst. web3x-codegen generates typings for contract ABIs either local, or remote from a simple configuration file called contracts.json.

Installing

yarn add -D web3x-codegen

Defining contracts.json

An example contracts.json looks like:

{
  "outputPath": "./src/contracts",
  "contracts": {
    "DaiContract": {
      "source": "etherscan",
      "net": "mainnet",
      "address": "0x89d24a6b4ccb1b6faa2625fe562bdd9a23260359"
    },
    "MyTruffleContract": {
      "source": "truffle",
      "buildFile": "../truffle-project/build/contracts/MyContract.json"
    },
    "MyRawAbiContract": {
      "source": "files",
      "abiFile": "../my-contract/abi.json",
      "initDataFile": "../my-contract/init-code.bin"
    }
  }
}

Run the code generator:

yarn web3x-codegen

The generator will create 3 contracts:

• For the first it uses etherscan to download the contract ABI and initialisation code at the given address, and generates the interface at ./src/contracts/DaiContract.ts.
• For the second it specifies a truffle build output and generates its interface at ./src/contracts/MyTruffleContract.ts.
• For the third it reads a raw ABI file and compiled initialisation code from local files, and generates its interface at ./src/contracts/MyRawAbiContract.ts. The initDataFile property is optional but you won't be able to easily deploy the contract without it.

For an example of the code generated, take a look at this example.

Using generated contracts

The following code demonstrates how to use the generated contract class. It's a similar API as used in web3.js, only now with type safety.

import { Address } from 'web3x/address';
import { fromWei } from 'web3x/utils';
import { WebsocketProvider } from 'web3x/providers';
import { Eth } from 'web3x/eth';
import { DaiContract } from './contracts/DaiContract';

const DAI_CONTRACT_ADDRESS = Address.fromString('0x89d24a6b4ccb1b6faa2625fe562bdd9a23260359');

async function main() {
  const provider = new WebsocketProvider('wss://mainnet.infura.io/ws');
  const eth = new Eth(provider);

  try {
    const contract = new DaiContract(eth, DAI_CONTRACT_ADDRESS);
    const daiBalance = await contract.methods.balanceOf(Address.ZERO).call();
    console.log(`Balance of 0 address DAI: ${fromWei(daiBalance, 'ether')}`);
  } finally {
    provider.disconnect();
  }
}

main().catch(console.error);

Deploying contracts is trivial as well, as the bytecode is imported by web3x-codegen and included as part of the contract class. The following code deploys an exact replica of the DAI contract on mainnet, only now you can mint your own funds.

import { Address } from 'web3x/address';
import { fromWei, toWei } from 'web3x/utils';
import { WebsocketProvider } from 'web3x/providers';
import { Eth } from 'web3x/eth';
import { DaiContract } from './contracts/DaiContract';

async function main() {
  const from = Address.fromString('0x903ddd91207f737255ca93eb5885c0e087be0fc3');
  const gasPrice = 50000;
  const provider = new WebsocketProvider('wss://mainnet.infura.io/ws');
  const eth = new Eth(provider);

  try {
    const contract = new DaiContract(eth);
    await contract
      .deploy('xf00f token')
      .send({ from, gasPrice })
      .getReceipt();
    await contract.methods
      .mint(toWei(1000, 'ether'))
      .send({ from, gasPrice })
      .getReceipt();
    const balance = await contract.methods.balanceOf(from).call();
    console.log(`Balance of ${from}: ${fromWei(balance, 'ether')}`);
  } finally {
    provider.disconnect();
  }
}

main().catch(console.error);

Packages

• web3x-codegen