Solidity Smart Contracts for OOP Developers

AmazingMessageRepeater.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.9.0;

import "./MessageRepeater.sol";

contract AmazingMessageRepeater is MessageRepeater {
     function repeatMessage(uint256 repetitions) public view virtual override returns (string[] memory){
        string[] memory arr;
        for (uint i = 0; i < repetitions; i++) {
            arr = addElementToStringArray(arr, toUpperCase(getMessage()));
            //arr.push(myMessage);
        } 

        return arr;
    }

    function toUpperCase(string memory str) private pure returns (string memory) {
        bytes memory strBytes = bytes(str);
        for (uint i = 0; i < strBytes.length; i++) {
            if (strBytes[i] >= 0x61 && strBytes[i] <= 0x7A) {
                strBytes[i] = bytes1(uint8(strBytes[i]) - 32);
            }
        }
        return string(strBytes);
    }
}

Messageable.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.9.0;

interface Messageable {
    function setMessage(string memory message) external;
    function getMessage() external returns (string memory) ;
    function getMessage(uint256 repetitions)  external returns (string[] memory );
    function repeatMessage(uint256 repetitions) external returns (string[] memory ) ;
}

MessageRepeater.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.9.0;

import "./Messageable.sol";

contract MessageRepeater is Messageable {
    string private myMessage;
    address private creator;
    constructor() {
        creator = msg.sender;
    }

    function setMessage(string memory message) public  {
        myMessage = message;
    }

    function getMessage() public view returns (string memory) {
        return myMessage;
    }

    function getMessage(uint256 repetitions) public view returns (string[] memory) {
        return repeatMessage(repetitions);
    }

    function repeatMessage(uint256 repetitions) public virtual view returns (string[] memory){
        string[] memory arr;
        for (uint i = 0; i < repetitions; i++) {
            arr = addElementToStringArray(arr, myMessage);
        } 

        return arr;
    }

    function addElementToStringArray(string[] memory oldArray, string memory newElement) internal  pure returns (string[] memory) {
        string[] memory newArray = new string[](oldArray.length + 1);
        for (uint i = 0; i < oldArray.length; i++) {
            newArray[i] = oldArray[i];
        }
        newArray[oldArray.length] = newElement;
        return newArray;
    }
}