ethereum - 所需气体超出区 block 气体限制回退功能

Question

我正在开发智能合约，并在此处观看了此视频:https://www.youtube.com/watch?v=s677QFT6e4U&t=911s 。我准确地复制了代码，但是当我尝试调用回退函数时，出现以下错误:所需气体超出区 block 气体限制:300000000。即使后备函数如下(它什么也不做):

function () payable {

}

这怎么可能使用过多的汽油？

契约(Contract)代码:

pragma solidity ^0.4.11;

import './IERC20.sol';
import './SafeMath.sol';

contract AToken is IERC20 {
    
    using SafeMath for uint256;
    
    uint256 public _totalSupply = 0;
    uint256 public constant hardLimit = 45000000;
    string public constant symbol = "ABC";
    string public constant name = "Alphabet";
    uint8 public constant decimals = 18;
    
    //1 ETH = 25000 Alphabet
    uint256 public constant RATE = 25000;
    
    address public owner;
    
    mapping(address => uint256) balances;
    mapping(address => mapping(address => uint256)) allowed;
    
    function () payable {
        createTokens();
    }
    
    function SnapToken() {
        owner = msg.sender;
    }
    
    function createTokens() payable {
        //require(msg.value > 0);
        //uint256 tokens = msg.value.mul(RATE);
        //require(tokens.add(_totalSupply) <= hardLimit);
        //balances[msg.sender] = balances[msg.sender].add(tokens);
        //_totalSupply = _totalSupply.add(tokens);
        //owner.transfer(msg.value);
    }
    
    function totalSupply() constant returns (uint256 totalSupply) {
        return _totalSupply;
    }
    
    function balanceOf(address _owner) constant returns (uint256 balance) {
        return balances[_owner];
    }
    
    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;
    }
    
    function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {
        require(allowed[_from][msg.sender] >= _value && balances[_from] >= _value && _value > 0);
        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(_value);
        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
        Transfer(_from, _to, _value);
        return true;
    }
    
    function approve(address _spender, uint256 _value) returns (bool success) {
        //allowed[msg.sender][_spender] = allowed[msg.sender][_spender].add(_value);
        Approval(msg.sender, _spender, _value);
        return true;
    }
    
    function allowance(address _owner, address _spender) constant returns (uint256 remaining) {
        return allowed[_owner][_spender];
    }
    event Transfer(address indexed _from, address indexed _to, uint256 _value);
    event Approval(address indexed _owner, address indexed _spender, uint256 value);
}

我注释掉了一些内容，看看这是否会减少气体需求，但不幸的是不会。您以前遇到过这种情况吗？

谢谢

Answer 1

正如发布的那样，合约在调用后备函数时会执行(在 Remix 中测试)。但是，一旦取消 createTokens()

中逻辑的注释，它将失败

后备函数的 Gas 限制较低 (2300)，因此其功能非常有限。您无法执行写入存储、调用外部函数或发送以太币等操作，因为您将立即达到限制。它主要用于使您的合约能够接收以太币并可能记录事件。

在上面发布的示例中，删除后备函数中对 createTokens() 的调用，然后直接从客户端调用该函数。

Documentation on Fallback Functions

客户端代码示例:

const abiDefinition = ...;
const contractAddress = ...;
const account = ...;
const amountInEther = ...;

const contract = web3.eth.contract(abiDefinition);
const contractInstance = contract.at(contractAddress);

const transactionObj = {
  from: account,
  value: web3.toWei(amountInEther, 'ether'),
};

contractInstance.createTokens.sendTransaction(transactionObj, (error, result) = {
  ...
};

此外，顺便说一句，您的值(value)计算不正确。 msg.value 采用 Wei，而不是以太。发送 1 以太币会使您远远超出您的硬限制。建议您在契约(Contract)中与 Wei 合作，因此您应该调整您的RATE。