first-solidity-project

What is Solidity?

Solidity is a programming language designed to build programs that run on the Ethereum virtual machine.

A Solidity program is called a contract. It consists of a layout of storage variables, an optional constructor function that produces additional bytecode for contract creation code, and a set of functions that are exposed to the world and can be called with the appropriate calldata sent with a user transaction or by another contract.

Solidity contracts can be developed using frameworks such as Brownie (Python) or hardhat (JavaScript)

For these demonstrations, we will use hardhat.

Creating a hardhat project

First, create a directory with a package.json file to declare a JavaScript module.

You will need the package hardhat

The modules hardhat-deploy and hardhat-deploy-ethers are also very common nowadays

Install with

yarn add hardhat hardhat-deploy hardhat-deploy-ethers

Then to make it a hardhat project, place the following code in hardhat.config.js at the root of the project

module.exports = {
  solidity: '0.8.10'
};

Now you can start writing contracts, placing them in the contracts/ directory at the root of your project.

To build your contracts, you simply execute

yarn hardhat compile

And it will produce a directory artifacts/ where your contract binaries will go, containing the bytecode for a deployment.

Contract artifacts also contain the abi property in their JSON, which contains a JSON definition of all of the contracts public functions, so you can construct objects in a JS environment that will expose methods to call the contract functions.

A Simple Contract

From the Solidity docs at https://docs.soliditylang.org/en/v0.8.10/introduction-to-smart-contracts.html:

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.4.16 <0.9.0;

contract SimpleStorage {
    uint storedData;

    function set(uint x) public {
        storedData = x;
    }

    function get() public view returns (uint) {
        return storedData;
    }
}

This is a contract that exposes a set(uint256) and get() function to get or set a storage variable called storedData.

We can build the contract as described in the previous section

yarn hardhat compile

To actually prove to ourselves that it works, we would want to be able to deploy the contract and then test the features.

We can do the former with hardhat-deploy

First, change your hardhat.config.js file to the following

require('hardhat-deploy')
require('hardhat-deploy-ethers')

module.exports = {
  solidity: '0.8.10'
}

When you include require statements at the top of your hardhat.config.js it will load any hardhat module you choose into the hardhat environment.

Loading hardhat modules typically alters the object that you get in a hardhat project when you do

const hre = require('hardhat'); // hre now contains the deployments property

To write our deployment file, we may use

// deploy/1_deploy.js

const hre = require('hardhat');

module.exports = async () => {
  const deployment = await hre.deployments.deploy('SimpleContract', {
    name: 'SimpleContract',
    args: [],
    libraries: {}
  });
  console.log('SimpleContract deployed to ' + deployment.address);
};