Gasless transactions via relayer example

This is a basic example project showing how to implement gasless meta-transactions via a Biconomy relayer and ERC2771Context.

Project setup

1. Clone the repo

git clone git@github.com:dabit3/gasless-transactions-example.git

2. Install dependencies

cd gasless-transactions-example

npm install

# or

yarn

3. Configure PRIVATE_KEY and INFURA_ENDPOINT environment variables in hardhat.config.js.

Also if you are deploying to a network other than Polygon, you can configure that information in hardhat.config.js.

4. Compile the project

npx hardhat compile

5. Deploy the smart contract

npx hardhat run scripts/deploy.js --network polygon

6. Update the greeterAddress in pages/index.js

Biconomy integration

1. Create an account on Biconomy

2. Create a new app. Choose the network you'd like to use (I deployed to Polygon).

3. Enter the smart contact address and ABI (ABI located at artifacts/contracts/Greeter/Greeter.sol/Greeter.json)

4. In Dapp APIs, add the setGreeting function

5. Create a .env.local file in the Next.js project and add the Biconomy API Key:

NEXT_PUBLIC_BICONOMY_API_KEY=your-api-key

6. Run the app

npm start

TLDR for implementing in existing app

1. Update contract to inherit from ERC2771Context

pragma solidity ^0.8.9;

import "@openzeppelin/contracts/metatx/ERC2771Context.sol";

contract Greeter is ERC2771Context {}

2. msg.sender -> _msgSender() - (though this contract does not use msg.sender)

3. Configure Biconomy app with contract address and methods you'd like to use

4. Update client-side code to use Biconomy SDKs