Scaffold-ETH Challenge: Building a Staking dApp (Part 1)

Introduction

In this guide, we’ll explore the first scaffold-ETH learning project: creating a staking dApp inspired by Ethereum 2.0’s staking contract.

Key Objectives

Allow users to stake ETH and track balances.
Prevent withdrawals once a deadline is reached or the staking threshold is met (funds are locked for future use, e.g., Ethereum POS).

What You’ll Learn

Setting up a scaffold-ETH project.
Writing a staking contract in Solidity.
Interacting with external contracts.
Creating unit tests for your contract.
Testing locally with React.
Deploying the contract to an Ethereum testnet.

Essential Resources

Project Setup

Clone and Configure

Clone the scaffold-eth repository:

git clone https://github.com/austintgriffith/scaffold-eth.git challenge-1-decentralized-staking
cd challenge-1-decentralized-staking
git checkout challenge-1-decentralized-staking
yarn install

Key Commands

Local Development:

yarn chain  # Starts Hardhat network (http://localhost:8545)
yarn start  # Launches React app (http://localhost:3000)
yarn deploy # Deploys contracts and refreshes the app

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Part 1: Implementing the `stake()` Function

Core Concepts

Payable Functions: Allow ETH transfers.
Mappings: Track user balances (address => uint256).
Events: Emit notifications for on-chain actions (e.g., Stake).

Code Implementation

Update Staker.sol:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;
import "hardhat/console.sol";
import "./ExampleExternalContract.sol";

contract Staker {
    ExampleExternalContract public exampleExternalContract;
    mapping(address => uint256) public balances;
    uint256 public constant threshold = 1 ether;
    event Stake(address indexed sender, uint256 amount);

    constructor(address exampleExternalContractAddress) {
        exampleExternalContract = ExampleExternalContract(exampleExternalContractAddress);
    }

    function stake() public payable {
        balances[msg.sender] += msg.value;
        emit Stake(msg.sender, msg.value);
    }
}

Testing Your Contract

Deploy the contract.
Fund your wallet via the Faucet.
Stake ETH (e.g., 0.5 ETH).
Verify:
- Balances update correctly.
- Events trigger in the UI.
- Contract balance reflects the stake.

FAQs

Q: Why isn’t my balance updating?
A: Ensure stake() is called with msg.value > 0 and the transaction succeeds.

Q: What’s the purpose of the threshold?
A: It’s the cap for total staked ETH (e.g., 1 ETH).

Q: How do I test events?
A: Check the browser console or use tools like Etherscan for testnets.