I'm new to ethereum. I followed a tutorial and I ended up with a contract that looks like this

pragma solidity ^0.4.15;
contract HelloWorld {
  uint public balance;

  function HelloWorld()  {
      balance = 1000;

  function deposit(uint _value)  returns (uint _newValue) {
      balance += _value;
      return balance;

After the contract is deployed at testrpc I try to call the deposit function with respect to the recent changes in syntax like so:

var hw = HelloWorld.deployed();
 return i.deposit(500)

but I get a Error: VM Exception while processing transaction: invalid opcode How do I call this function?



You should do it like this:

      .then(instance => {
        return instance.deposit(500,{
          from: this.account
      .then(result => {
      .catch(e => {
  • Thanks Pablo! However, if I do it like that I get 'Error: invalid address'. If I replace this.account with web3.eth.accounts[0] i get 'invalid opcode' again. – vlad Oct 14 '17 at 13:58
  • Yes, sorry, I assumed you had assigned this.account to web3.eth.accounts[0]. Then, there must be a problem with the contract. Is that all the code there is to it? – pabloruiz55 Oct 14 '17 at 14:04
  • That's all the code. I just discovered ether does get subtracted from the account, even though there's that error msg (opcode) – vlad Oct 14 '17 at 14:13
  • 2
    ok, it was stupid. I just restarted testrpc, recompiled and migrated the contract again, and now it works. – vlad Oct 14 '17 at 15:27

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