Swap ether to ERC20 token

Question

I have a dex contract and i want to swap ether with an ERC20 token, when i call a swap function a get this error:

Gas estimation errored with the following message (see below). The transaction execution will likely fail. Do you want to force sending? execution reverted: ERC20: transfer amount exceeds balance { "originalError": { "code": 3, "data": "0x08c379a00000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000002645524332303a207472616e7366657220616d6f756e7420657863656564732062616c616e63650000000000000000000000000000000000000000000000000000", "message": "execution reverted: ERC20: transfer amount exceeds balance" } }

But i have enough ether for calling this function(as much as msg.value).

Here is my swap function:

function _swapWithEth () external payable {
        require(msg.value > 0 , "Amount zero");

        uint _amountInWithFee = (msg.value * 995) / 1000;
        
        uint256 ethPrice = getEthPrice();
        _amountOut =(_amountInWithFee * ethPrice / price);

        MYToken.transfer(msg.sender, _amountOut);

    }

Anyone know what's wrong? Thanks

Answer 1

It looks like the _swapWithEth function is trying to transfer an ERC20 token to the sender, but the transfer is failing because the sender does not have enough balance to cover the amount being transferred.

The error message ERC20: transfer amount exceeds balance indicates that the sender's balance of the ERC20 token is less than the amount being transferred.

To fix this issue, you can either make sure that the sender has enough balance of the ERC20 token to cover the transfer, or you can modify the function to check the sender's balance before making the transfer and return an error if the balance is insufficient.

Here is an example of how you could modify the _swapWithEth function to check the sender's balance before making the transfer:

function _swapWithEth() external payable {
  require(msg.value > 0, "Amount zero");

  uint _amountInWithFee = (msg.value * 995) / 1000;
        
  uint256 ethPrice = getEthPrice();
  _amountOut =(_amountInWithFee * ethPrice / price);

  // Check the sender's balance before making the transfer
  require(MYToken.balanceOf(msg.sender) >= _amountOut, "Insufficient balance");

  // Make the transfer if the sender has enough balance
  MYToken.transfer(msg.sender, _amountOut);
}

This modification will check the sender's balance of the ERC20 token before making the transfer, and return an error if the balance is insufficient. This should prevent the transaction from failing with the ERC20: transfer amount exceeds balance error.