Welcome to our beginners guide to Decimal smart chain contracts and dApp development. This Tutorial has the goal to quickly teach you how to write and deploy smart contract to decimal smart chain.

In this tutorial we will use:

• Solidity
• JavaScript
• Node.js
• Ethers.js
• Hardhat

Setting up environment​

In a first step we need to install Node.js.

Installing Node.js​

You can skip this section if you already have a working Node.js >= 16.0

Paste this commands in a terminal:​

Ubuntu

sudo apt update
sudo apt install curl git
curl -fsSL https://deb.nodesource.com/setup_18.x | sudo -E bash -
sudo apt-get install -y nodejs

MacOS

curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.1/install.sh | bash
nvm install 18
nvm use 18
nvm alias default 18
npm install npm --global # Upgrade npm to the latest version

Windows

To install Node.js on windows follow this guide: 
https://docs.microsoft.com/en-us/windows/dev-environment/javascript/nodejs-on-windows

Creating a new hardhat project​

Open a new terminal and run this commands to create a new folder

Creating a new folder

mkdir hardhat-tutorial
cd hardhat-tutorial

Install hardhat and run it:

npm install –save-dev hardhat
npm install –save-dev @nomicfoundation/hardhat-toolbox
npx hardhat

Select Create an empty hardhat.config.js with your keyboard and hit enter. Hardhat.config.js is usually located in the project root folder and contains the entirety of your setup.

Writing smart contract​

Let's start by creating a new folder in our hardhat project named contracts. In this folder we create file named token.sol.

Put this code into the file:​

contracts/token.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;
 
contract ExampleContract {
   mapping(address => uint256) balances;
 
   event Deposit(uint256 value);
   event Withdraw(address indexed receiver, uint256 value);
 
   constructor() {}
 
   function deposit() external payable {
       balances[msg.sender] += msg.value;
       emit Deposit(msg.value);
   }
 
   function withdrawNative(address payable receiver, uint256 amount) public {
       require(amount >= balances[msg.sender], "Insufficient balance");
       balances[msg.sender] -= amount;
 
       sendNative(receiver, amount);
 
       emit Withdraw(receiver, amount);
   }
 
   function sendNative(address payable account, uint256 amount) private {
       (bool sent, ) = account.call{gas: 10000, value: amount}("");
       require(sent, "Failed to send DEL");
   }
 
   receive() external payable {}
}

To compile the contract run npx hardhat compile in your terminal.

Contract compilation

npx hardhat compile
Compiled 1 Solidity file successfully

Deploying to the Decimal smart chain​

So you are ready to test your contract on a real network, this way others get access to your code and can check it.

In real Decimal smart chain “mainnet” you must pay for transaction in real money, but there is a separate “devnet” network, which mimics real world scenarios without putting real money at stake.

At the software level, deploying to the devnet is the same as deploying to the mainnet. The only difference is which network you connect to. Let's look into what the code to deploy your contracts using ethers.js would look like.

Lets create a new folder inside the root of the project named scripts and create file named deploy.js there.

Put this code into the file:​

scripts/deploy.js

async function main() {
   const accounts = await ethers.getSigners();
   console.log('Deploying contract with account:', accounts[0].address);
 
   const balance = await  accounts[0].getBalance();
   console.log('Account balance ',balance.toString());
 
   const ExampleContract = await ethers.getContractFactory("ExampleContract");
 
   const exampleContract = await ExampleContract.connect(accounts[0]).deploy();
   await exampleContract.deployed();
 
   console.log('ExampleContract address:', example.address);
}
 
main()
 .then(() => process.exit(0))
 .catch((error) => {
   console.error(error);
   process.exit(1);
 });

To tell Hardhat which network do you want connect to, you use the --network parameter when running any task, like this:

Network connection

npx hardhat run scripts/deploy.js –network <network-name>

With our configuration, running it without –network parameter will deploy contract in the local Hardhat Network. The deployment gets lost after execution, but it is still useful for testing our deployment code.

Deploy in the local hardhat network

npx hardhat run scripts/deploy.js –network <network-name>

To deploy in a remote network such as mainnet or devnet, you need to configure network entry in your hardhat.config.js file. We will use devnet for this example.

Put this code into hardhat.config.js.​

hardhat.config.js

require("@nomicfoundation/hardhat-toolbox");
 
const PRIVATE_KEY = "YOUR PRIVATE KEY";
 
module.exports = {
  solidity: {
    version: "0.8.17",
    settings: {
      optimizer: {
        enabled: true,
        runs: 200,
      },
    },
  },
  defaultNetwork: "decimal_devnet",
  networks: {
    decimal_devnet: {
      url: `https://devnet-val.decimalchain.com/web3/`,
      accounts: [PRIVATE_KEY],
      gasPrice: 80000000000000
    }
  }
};

To deploy on Decimal devnet you need to send some devnet DEL to the address that's going to be making the deployment. You can get devnet DEL from a faucet, a service that distributes devnet DEL for free.

Finally, run:

Deploy to live network

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

If everything went well, you should see the deployed contract address.