transfer function in ERC20 token returning false

Question

I've created a test ERC20 token like at https://theethereum.wiki/w/index.php/ERC20_Token_Standard. I've sent some test ether to the contract and can verify my account has some of the token, eg with the following command (calling the "balanceOf" function):

contractInstance.balanceOf.call(web3.eth.accounts[0])

returns:

{ [String: '7000000000000000'] s: 1, e: 15, c: [ 70 ] }

After that I want to send some of the token to another account. My transfer function is as follows:

function transfer(address _to, uint256 _value) returns (bool success) {
           require(balances[msg.sender] >= _value && _value > 0);
           balances[msg.sender] = balances[msg.sender].sub(_value);
           balances[_to] = balances[_to].add(_value);
           Transfer(msg.sender, _to, _value);
           return true;
       }

(I'm using the SafeMath.sol contract at https://github.com/OpenZeppelin/zeppelin-solidity/blob/master/contracts/math/SafeMath.sol)

Running the following command to execute the transfer function and send some of the token to my second account:

contractInstance.transfer.call(web3.eth.accounts[1], 0.005)

returns

false

So the transfer isn't being executed. What might the issue be here?

Answer 1

Three possible issues I spotted taking a quick glance.

Your second argument is "0.005", which is not an int, so it won't be possible to cast it to a uint256 as you requested. If you followed the tutorial, you probably also used 18 decimals to define your contract's token-decimals. You'll need to multiply "0.005" by 10^18. quick trick: as 1 ether is also 1*(10^18) wei, you can just replace your "0.005" with web3.toWei("0.005").

In your call function, also provide an object to specify the sender.

{ from: web3.eth.accounts[0] }

Also, when calling non-constant methods, you don't need the .call part, so this should work.

contractInstance.transfer(web3.eth.accounts[1], web3.toWei(0.005), { from: web3.eth.accounts[0] })