How to return a storage array from a Solidity function?

Question

I wrote a very simple smart-contract where I want to create an external function which returns as an output a storage array which contains the following items [0,2,4,6,8,10,12,14,16,18]:

pragma solidity ^0.8.0;

contract MyContract {

    uint[] myArray;

    function myFunc() external returns(uint[] memory){

        for(uint i=0; i<10; i++){
            myArray[i] = i*2;
        }
    
        return myArray;
    }

}

However once I deploy it on the Ganache blockchain via truffle (truffle migrate) and i open the truffle console (truffle console) and type the following lines of code:

MyContract.deployed().then(function(i) { contract=i; })

contract.myFunc()

I get this error:

Uncaught Error: Returned error: VM Exception while processing transaction: revert
    at evalmachine.<anonymous>:0:10
    at sigintHandlersWrap (vm.js:273:12)
    at Script.runInContext (vm.js:140:14)
    at runScript (C:\Users\feder\AppData\Roaming\npm\node_modules\truffle\build\webpack:\packages\core\lib\console.js:270:1)
    at Console.interpret (C:\Users\feder\AppData\Roaming\npm\node_modules\truffle\build\webpack:\packages\core\lib\console.js:285:1)
    at bound (domain.js:413:15)
    at REPLServer.runBound [as eval] (domain.js:424:12)
    at REPLServer.onLine (repl.js:817:10)
    at REPLServer.emit (events.js:315:20)
    at REPLServer.EventEmitter.emit (domain.js:467:12)
    at REPLServer.Interface._onLine (readline.js:337:10)
    at REPLServer.Interface._line (readline.js:666:8)
    at REPLServer.Interface._ttyWrite (readline.js:1010:14)
    at REPLServer.self._ttyWrite (repl.js:907:9) {
  data: {
    '0x9aa71a7a511b486ff55a74ab556e9c22eb420ea4991a206087051cd9ae08ca94': {
      error: 'revert',
      program_counter: 163,
      return: '0x4e487b710000000000000000000000000000000000000000000000000000000000000032'
    },
    stack: 'RuntimeError: VM Exception while processing transaction: revert\n' +
      '    at Function.RuntimeError.fromResults (C:\\Program Files\\WindowsApps\\GanacheUI_2.5.4.0_x64__5dg5pnz03psnj\\app\\resources\\static\\node\\node_modules\\ganache-core\\lib\\utils\\runtimeerror.js:94:13)\n' +
      '    at BlockchainDouble.processBlock (C:\\Program Files\\WindowsApps\\GanacheUI_2.5.4.0_x64__5dg5pnz03psnj\\app\\resources\\static\\node\\node_modules\\ganache-core\\lib\\blockchain_double.js:627:24)\n' +
      '    at processTicksAndRejections (internal/process/task_queues.js:93:5)',
    name: 'RuntimeError'
  },
  hijackedStack: 'Error: Returned error: VM Exception while processing transaction: revert\n' +
    '    at Object.ErrorResponse (C:\\Users\\feder\\AppData\\Roaming\\npm\\node_modules\\truffle\\build\\webpack:\\node_modules\\web3-core-helpers\\lib\\errors.js:28:1)\n' +     
    '    at C:\\Users\\feder\\AppData\\Roaming\\npm\\node_modules\\truffle\\build\\webpack:\\node_modules\\web3\\node_modules\\web3-core-requestmanager\\lib\\index.js:303:1\n' + 
    '    at C:\\Users\\feder\\AppData\\Roaming\\npm\\node_modules\\truffle\\build\\webpack:\\packages\\provider\\wrapper.js:107:1\n' +
    '    at XMLHttpRequest.request.onreadystatechange (C:\\Users\\feder\\AppData\\Roaming\\npm\\node_modules\\truffle\\build\\webpack:\\node_modules\\web3\\node_modules\\web3-providers-http\\lib\\index.js:98:1)\n' +
    '    at XMLHttpRequestEventTarget.dispatchEvent (C:\\Users\\feder\\AppData\\Roaming\\npm\\node_modules\\truffle\\build\\webpack:\\node_modules\\xhr2-cookies\\dist\\xml-http-request-event-target.js:34:1)\n' +
    '    at XMLHttpRequest.exports.modules.996763.XMLHttpRequest._setReadyState (C:\\Users\\feder\\AppData\\Roaming\\npm\\node_modules\\truffle\\build\\webpack:\\node_modules\\xhr2-cookies\\dist\\xml-http-request.js:208:1)\n' +
    '    at XMLHttpRequest.exports.modules.996763.XMLHttpRequest._onHttpResponseEnd (C:\\Users\\feder\\AppData\\Roaming\\npm\\node_modules\\truffle\\build\\webpack:\\node_modules\\xhr2-cookies\\dist\\xml-http-request.js:318:1)\n' +
    '    at IncomingMessage.<anonymous> (C:\\Users\\feder\\AppData\\Roaming\\npm\\node_modules\\truffle\\build\\webpack:\\node_modules\\xhr2-cookies\\dist\\xml-http-request.js:289:47)\n' +
    '    at IncomingMessage.emit (events.js:327:22)\n' +
    '    at IncomingMessage.EventEmitter.emit (domain.js:529:15)\n' +
    '    at endReadableNT (internal/streams/readable.js:1327:12)\n' +
    '    at processTicksAndRejections (internal/process/task_queues.js:80:21)'
}

Does anyone know what I am doing wrong? How can I solve this issue and get the result I want?

Answer 1

to push item to array use .push() on array , in this way it's semms to work :
myArray.push(i*2);

;)