Project Setup Using Hardhat & Truffle — part 3

Now we will write a simple smart contract and deploy it to our local blockchain

Writing the smart contract

We can ignore the existing contract for now but feel free to explore them

For both Truffle and Hardhat, we can create a new file inside the contract folder

Solidity is the language that will be used for our example. More information about it can be found HERE

• Name it

NumberChanger.sol

• Declare the SPDX-License with it being commented out

// SPDX-License-Identifier: MIT

• Define the version of Solidity the contract will be complied in, we will set it to the version to be the same as in our config file

This allows it to be compiled with version 0.8.6 or higher

pragma solidity ^0.8.6;

• Write our contract by first declaring it and giving it the same name as our file name

/ SPDX-License-Identifier: MIT
pragma solidity ^0.8.6;

contract NumberChanger {
}

• Declare a state variable called number

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.6;

contract NumberChanger {
uint256 number;
}

• Create a function that will retrieve the number stored in the state variable

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.6;
contract NumberChanger {
uint256 number;
function getNumber() public views returns(uint256) {
return number;
  }
}

• Create a function that updates the number in state variable

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.6;
contract NumberChanger {
uint256 number;
function getNumber() public views returns(uint256) {
return number;
}
function setNumber(uint256 _number) public {
number = _number;
 }
}

We now have written a smart contract that allows the number to be stored and updated on the blockchain

Hardhat

Hardhat allows the option to console log in Solidity, in order to do so

• Import hardhat/console.sol after the version of Solidity has been declared

import "hardhat/console.sol"
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.6;
import "hardhat/console.sol"

• Add it to where you would like to see an output

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.6;
import "hardhat/console.sol";
contract NumberChanger {
uint256 number;
function getNumber() public view returns(uint256) {
return number;
}
function setNumber(uint256 _number) public {
number = _number;
console.log(number)
 }
}

The import of hardhat/console.sol and use of console.log is optional only if you are using Hardhat

The finished contract should look like this

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.6;
contract NumberChanger {
uint256 number;
function getNumber() public view returns(uint256) {
return number;
}
function setNumber(uint256 _number) public {
number = _number;
 }
}

In part 4 we will deploy our contract to the local blockchain. Click here for part 4.

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