I have a token created using OpenZeppelin library. I use the CappedToken contract.

My code is :

pragma solidity ^0.4.18;

import 'openzeppelin-solidity/contracts/token/ERC20/CappedToken.sol';

contract YLBToken is CappedToken {
    string public name = "My Token Beta";
    string public symbol = "MTB";
    uint8 public decimals = 18;

    function YLBToken(uint256 cap) CappedToken(cap) {

Using truffle I compile and test it. I migrated to Ropsten.

I created a web page to run it.

        <script src="https://cdn.jsdelivr.net/gh/ethereum/web3.js/dist/web3.min.js"></script>
        <script type='text/javascript'>
            var deployedContract;
            const ADDRESS = "0xcbcc819866a24a777b0c076d4922c127de9ecb06";
            const ABI = MY_ABI;

            // Init and detect metamask
            window.addEventListener('load', function () {
                if (typeof web3 !== 'undefined') {
                    web3 = new Web3(web3.currentProvider);
                    currentAccount = web3.eth.accounts[0];
                } else {
                    // set the provider you want from Web3.providers
                    web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:7545"));
                    console.log("Metamask or similar not detected");

                deployedContract = web3.eth.contract(ABI).at(ADDRESS);
                deployedContract.mint(currentAccount, parseInt(1000) * 1000000000000000000, { from: currentAccount, gasPrice: web3.toWei(1, 'gwei') }, function (error, result) {
                    if (!error) {
                        console.log("Mint result = " + result);
                    else {

I expect Metamask to open and after clicking submit to mint 1000 tokens on the owner address, just to test is working fine. I have it running into a webserver.

But this is what Metamask shows :

Metamask showing the message "Transaction error. Exception thrown in contract code

I have no clue why Metamask shows this message. Using truffle test the mint function works fine. Using Metamask pointing to localhost:8545 and running testrpc in a console also worked fine.

Can someone point me to a solution?

1 Answer 1


Answering my own question:

The message "Transaction error. Exception thrown in contract code" appears when some of the "requires" in your solidity code is triggered.

In my case, I was setting a cap in the migration file of truffle of 10.000 and when minting I was using :

parseInt(1000) * 1000000000000000000

because of the 18 decimals.

So 100000000000000000000000 > cap and the error was thrown

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