错误：处理事务时出现 VM 异常：还原

Question

当我将一些代币转移到去中心化银行时出现此错误 这是代码

测试.js：

 await decentralbank.stakeTokens(tokens("100"), {
    from: customer,
  });

DecentralBank.sol:

function stakeTokens(uint256 _amount) public {


    tether.transferFrom(msg.sender, address(this), _amount);

    // update staking balance
    stakingBalance[msg.sender] = stakingBalance[msg.sender] + _amount;

    // add user to stakers array *only* if they haven't staked already
    if (!hasStaked[msg.sender]) {
        stakers.push(msg.sender);
    }

    // update stakng status
    isStaking[msg.sender] = true;
    hasStaked[msg.sender] = true;
}

系绳溶胶：

 function transferFrom(
    address _from,
    address _to,
    uint256 _value
) public  returns  (bool success) {
    require(_value <= balanceOf[_from]);
    require(_value <= allowance[_from][msg.sender]);
    balanceOf[_from] -= _value;
    balanceOf[_to] += _value;
    allowance[_from][msg.sender] -= _value;
    emit Transfer(_from, _to, _value);
    return true;
}

Answer 1

通过查看，我猜你忘记了在调用stakeTokens之前批准令牌传输。

await tether.approve(decentralbank.address, tokens("100"), {
  from: costumer,
});

await decentralbank.stakeTokens(tokens("100"), {
  from: customer,
});

另外，一个安全注意事项，你应该在合同中的所有 state 更改之前调用transferFrom以避免重入攻击，或者你可以只使用这个库。