Returned error: VM Exception while processing transaction: revert ERC20: transfer amount exceeds balance

Question

MyCode Like this:

// SPDX-License-Identifier: GPL-3.0

pragma solidity >=0.7.0 <0.9.0;

import "./INToken.sol";
import "./Console.sol";

contract TransferCoin is Console {

    // 这个状态变量存储在区块链网络上
    address public owner;
    INToken public coin;

    constructor(address _coinAddress) {
        // 合约拥有者为合约创建者
        owner = msg.sender;
        // 设置映币地址
        coin = INToken(_coinAddress);
    }

    function trans(address _to, uint256 _amount) public {
        log("_to", _to);
        log("_amount", _amount);
        coin.transfer(_to, _amount);
    }
}

when i try to use trans function, the error: transact to TransferCoin.trans errored: Returned error: VM Exception while processing transaction: revert ERC20: transfer amount exceeds balance.
but my account's balance is 99999596.
Can anyone help me tell me how to solve this problem， thanks.

Answer 1

In TransferCoin::trans function, you are calling coin.transfer(_to, _amount), since your INtoken contract inherit from Openzeppelin ERC20, transfer implementation use msg.sender It means that it's a transfer from your TransferCoin contract balance.

Please see differences between tx.origin and msg.sender

Maybe you should take a look at delegatecall

Answer 2

Make sure your contract has enough INToken balance. Try this, https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/ERC20.sol#L158

coin.transferFrom(address(this), _to, _amount);