invalid opcode error with a simple Solidity contract and script

Question

I am a newcomer to Solidity and web3.js . I am following the tutorial here -

https://medium.com/@mvmurthy/full-stack-hello-world-voting-ethereum-dapp-tutorial-part-1-40d2d0d807c2

to build a simple Voting Dapp. I've installed ganache-cli, solc and web3 version 0.20.2 in the local node_modules folder using npm. The Voting.sol contract in Solidity is :

pragma solidity ^0.4.18;

contract Voting {

  mapping (bytes32 => uint8) public votesReceived;
  bytes32[] public candidateList;

  function Voting(bytes32[] candidateNames) public {
    candidateList = candidateNames;
  }

  function totalVotesFor(bytes32 candidate) view public returns (uint8) {
    return votesReceived[candidate];
  }
}

with the following script called voting_main.js:

Web3 = require('web3')
web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"))

fs = require('fs')
code = fs.readFileSync('Voting.sol').toString()

solc = require('solc')
compiledCode = solc.compile(code)

abiDefinition = JSON.parse(compiledCode.contracts[':Voting'].interface)
VotingContract = web3.eth.contract(abiDefinition)
byteCode = compiledCode.contracts[':Voting'].bytecode
deployedContract = VotingContract.new(['Rama','Nick','Jose'],{data: byteCode, from: web3.eth.accounts[0], gas: 4700000})
contractInstance = VotingContract.at(deployedContract.address)

contractInstance.totalVotesFor.call('Rama')

When I run ganache-cli on localhost:8545 and then run the script in another terminal, I get the following error.

ameya@ameya-HP-ENVY-15-Notebook-PC:~/Fresh_install$ node voting_main.js 
/home/ameya/Fresh_install/node_modules/solc/soljson.js:1
(function (exports, require, module, __filename, __dirname) { var Module;if(!Module)Module=(typeof Module!=="undefined"?Module:null)||{};var moduleOverrides={};for(var key in Module){if(Module.hasOwnProperty(key)){moduleOverrides[key]=Module[key]}}var ENVIRONMENT_IS_WEB=typeof window==="object";var ENVIRONMENT_IS_WORKER=typeof importScripts==="function";var ENVIRONMENT_IS_NODE=typeof process==="object"&&typeof require==="function"&&!ENVIRONMENT_IS_WEB&&!ENVIRONMENT_IS_WORKER;var ENVIRONMENT_IS_SHELL=!ENVIRONMENT_IS_WEB&&!ENVIRONMENT_IS_NODE&&!ENVIRONMENT_IS_WORKER;if(ENVIRONMENT_IS_NODE){if(!Module["print"])Module["print"]=function print(x){process["stdout"].write(x+"\n")};if(!Module["printErr"])Module["printErr"]=function printErr(x){process["stderr"].write(x+"\n")};var nodeFS=require("fs");var nodePath=require("path");Module["read"]=function read(filename,binary){filename=nodePath["normalize"](filename);var ret=nodeFS["readFileSync"](filename);if(!r

Error: VM Exception while processing transaction: invalid opcode
    at Object.InvalidResponse (/home/ameya/Fresh_install/node_modules/web3/lib/web3/errors.js:38:16)
    at RequestManager.send (/home/ameya/Fresh_install/node_modules/web3/lib/web3/requestmanager.js:61:22)
    at Eth.send [as call] (/home/ameya/Fresh_install/node_modules/web3/lib/web3/method.js:145:58)
    at SolidityFunction.call (/home/ameya/Fresh_install/node_modules/web3/lib/web3/function.js:135:32)
    at Object.<anonymous> (/home/ameya/Fresh_install/voting_main.js:16:32)
    at Module._compile (internal/modules/cjs/loader.js:654:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:665:10)
    at Module.load (internal/modules/cjs/loader.js:566:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:506:12)
    at Function.Module._load (internal/modules/cjs/loader.js:498:3)

This seems to be a very simple example which is still throwing the invalid opcode error. Where am I going wrong ?

Answer 1

You don't need to call .at() if you're using .new(). You use at() when you want to interact with a contract that has already been deployed to the blockchain.

If you choose to deploy a new contract, you should use the async version of the method call (synchronous is no longer supported in web3j 1.0). Your call should be something like this:

VotingContract.new(['Rama','Nick','Jose'],{data: byteCode, from: web3.eth.accounts[0], gas: 4700000}, (error, deployedContract) => {
    if (!error) {
        if (deployedContract.address) {
            console.log(deployedContract.totalVotesFor.call('Rama'));
        }
    }
});

Note that the callback is fired twice. First time is for the submission of the transaction (deployedContract.transactionHash will be set) and the second time after the transaction is mined.

You can also look at the example in the web3js docs (pasted below for convenience).

const fs = require("fs");
const solc = require('solc')

let source = fs.readFileSync('nameContract.sol', 'utf8');
let compiledContract = solc.compile(source, 1);
let abi = compiledContract.contracts['nameContract'].interface;
let bytecode = compiledContract.contracts['nameContract'].bytecode;
let gasEstimate = web3.eth.estimateGas({data: bytecode});
let MyContract = web3.eth.contract(JSON.parse(abi));

var myContractReturned = MyContract.new(param1, param2, {
   from:mySenderAddress,
   data:bytecode,
   gas:gasEstimate}, function(err, myContract){
    if(!err) {
       // NOTE: The callback will fire twice!
       // Once the contract has the transactionHash property set and once its deployed on an address.

       // e.g. check tx hash on the first call (transaction send)
       if(!myContract.address) {
           console.log(myContract.transactionHash) // The hash of the transaction, which deploys the contract

       // check address on the second call (contract deployed)
       } else {
           console.log(myContract.address) // the contract address
       }

       // Note that the returned "myContractReturned" === "myContract",
       // so the returned "myContractReturned" object will also get the address set.
    }
  });