helloworld.sol

gistfile1.txt

// The source code is for Solidity version
// greater than 0.7.0
pragma solidity >=0.7.0 <0.9.0;

// https://github.com/OpenZeppelin/openzeppelin-contracts
import "@openzeppelin/contracts/access/Ownable.sol";

// Starts the contract
contract HelloWorld is Ownable {
    // The keyword "public" makes variables
    // accessible from other contracts
    string public message;
    
    // Constructor code runs when the contract is completed
    constructor(string memory firstMessage) {
        message = firstMessage;
    }
    
    function update(string memory newMessage) public onlyOwner {
        message = newMessage;
    }
    
    // getter
    function getMessage() public view returns (string memory) {
        return message;
    }
}