使用BNB从合同中购买代币时出现的问题

Question

我正在创建这个智能合约，它创建并将所有代币添加到我的钱包中。然后我把钱包里的所有代币都发给我的合同。

然而，当我从另一个钱包为合同发送BNB时，我想让他退还我合同中的一些代币。

当我这样做时，传输失败并发送以下错误消息：

警告！合同执行过程中遇到错误[气体耗尽]

Queria saber是一种错误的方法，你可以用它来对抗天然气。

交易详细信息：https://testnet.bscscan.com/tx/0x7ef36e49e3c6f77716aee79cefbde6c298c3ddeef16ed12dbe613573661135bb

智能合约：

pragma solidity ^0.8.0;
interface IERC20 {
function totalSupply() external view returns (uint256);
function balanceOf(address account) external view returns (uint256);
function allowance(address owner, address spender) external view returns (uint256);
function transfer(address recipient, uint256 amount) external returns (bool);
function approve(address spender, uint256 amount) external returns (bool);
function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

event Transfer(address indexed from, address indexed to, uint256 value);
event Approval(address indexed owner, address indexed spender, uint256 value); }

contract ERC20Basic is IERC20 {
string public constant name = "ByeSeel";
string public constant symbol = "BYS";
uint8 public constant decimals = 18;

event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
event Transfer(address indexed from, address indexed to, uint tokens);

mapping(address => uint256) balances;
mapping(address => mapping (address => uint256)) allowed;
uint256 totalSupply_ = 100 * 10 ** 18;
using SafeMath for uint256;
constructor() public {
balances[msg.sender] = totalSupply_;
}
function totalSupply() public override view returns (uint256) {
return totalSupply_;
}
function balanceOf(address tokenOwner) public override view returns (uint256) {
return balances[tokenOwner];
}
function transfer(address receiver, uint256 numTokens) public override returns (bool) {
require(numTokens <= balances[msg.sender]);
balances[msg.sender] = balances[msg.sender].sub(numTokens);
balances[receiver] = balances[receiver].add(numTokens);
emit Transfer(msg.sender, receiver, numTokens);
return true;
}
function approve(address delegate, uint256 numTokens) public override returns (bool) {
allowed[msg.sender][delegate] = numTokens;
emit Approval(msg.sender, delegate, numTokens);
return true;
}
function allowance(address owner, address delegate) public override view returns (uint) {
return allowed[owner][delegate];
}
function transferFrom(address owner, address buyer, uint256 numTokens) public override returns (bool) {
require(numTokens <= balances[owner]);
require(numTokens <= allowed[owner][msg.sender]);
balances[owner] = balances[owner].sub(numTokens);
allowed[owner][msg.sender] = allowed[owner][msg.sender].sub(numTokens);
balances[buyer] = balances[buyer].add(numTokens);
emit Transfer(owner, buyer, numTokens);
return true;
}
event Received(address, uint);
receive() external payable {
emit Received(msg.sender, msg.value);
}
}
library SafeMath {
function sub(uint256 a, uint256 b) internal pure returns (uint256) {
assert(b <= a);
return a - b;
}
function add(uint256 a, uint256 b) internal pure returns (uint256) {
uint256 c = a + b;
assert(c >= a);
return c;
} }
contract DEX {
event Bought(uint256 amount);
event Sold(uint256 amount);

IERC20 public token;
constructor() public {
token = new ERC20Basic();
}
function buy() payable public {
uint256 amountTobuy = msg.value;
uint256 dexBalance = token.balanceOf(address(this));
require(amountTobuy > 0, "You need to send some Ether");
require(amountTobuy <= dexBalance, "Not enough tokens in the reserve");
token.transfer(msg.sender, amountTobuy);
emit Bought(amountTobuy);
}
function sell(uint256 amount) public {
require(amount > 0, "You need to sell at least some tokens");
uint256 allowance = token.allowance(msg.sender, address(this));
require(allowance >= amount, "Check the token allowance");
token.transferFrom(msg.sender, address(this), amount);
msg.sender.transfer(amount);
emit Sold(amount);
}
}

Answer 1

根据BscScan上的交易详细信息，您试图发送0.1 BNB，但没有调用任何函数。

您的合约没有receive((函数，也没有fallback((函数来接受传入的BNB。

因此，您所需要做的就是实现receive()函数。注意允许此函数接受BNB的payable修饰符。

contract ERC20Basic is IERC20 {
// rest of your code
receive() external payable {
// can call the buy() function
buy();
}
}

您可以在屏幕截图中看到，当您向合同发送100 wei(在BNB的情况下为100 jager(时，receive()函数执行buy()函数并生成Bought事件日志。

以下是在您的合同中实现的全部代码：

pragma solidity ^0.8.0;
interface IERC20 {
function totalSupply() external view returns (uint256);
function balanceOf(address account) external view returns (uint256);
function allowance(address owner, address spender) external view returns (uint256);
function transfer(address recipient, uint256 amount) external returns (bool);
function approve(address spender, uint256 amount) external returns (bool);
function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

event Transfer(address indexed from, address indexed to, uint256 value);
event Approval(address indexed owner, address indexed spender, uint256 value);

}

contract ERC20Basic is IERC20 {
string public constant name = "ByeSeel";
string public constant symbol = "BYS";
uint8 public constant decimals = 18;

//event Approval(address indexed tokenOwner, address indexed spender, uint tokens);
//event Transfer(address indexed from, address indexed to, uint tokens);

mapping(address => uint256) balances;
mapping(address => mapping (address => uint256)) allowed;
uint256 totalSupply_ = 100 * 10 ** 18;
using SafeMath for uint256;
constructor() public {
balances[msg.sender] = totalSupply_;
}
function totalSupply() public override view returns (uint256) {
return totalSupply_;
}
function balanceOf(address tokenOwner) public override view returns (uint256) {
return balances[tokenOwner];
}
function transfer(address receiver, uint256 numTokens) public override returns (bool) {
require(numTokens <= balances[msg.sender]);
balances[msg.sender] = balances[msg.sender].sub(numTokens);
balances[receiver] = balances[receiver].add(numTokens);
emit Transfer(msg.sender, receiver, numTokens);
return true;
}
function approve(address delegate, uint256 numTokens) public override returns (bool) {
allowed[msg.sender][delegate] = numTokens;
emit Approval(msg.sender, delegate, numTokens);
return true;
}
function allowance(address owner, address delegate) public override view returns (uint) {
return allowed[owner][delegate];
}
function transferFrom(address owner, address buyer, uint256 numTokens) public override returns (bool) {
require(numTokens <= balances[owner]);
require(numTokens <= allowed[owner][msg.sender]);
balances[owner] = balances[owner].sub(numTokens);
allowed[owner][msg.sender] = allowed[owner][msg.sender].sub(numTokens);
balances[buyer] = balances[buyer].add(numTokens);
emit Transfer(owner, buyer, numTokens);
return true;
}
event Received(address, uint);
receive() external payable {
emit Received(msg.sender, msg.value);
}
}
library SafeMath {
function sub(uint256 a, uint256 b) internal pure returns (uint256) {
assert(b <= a);
return a - b;
}
function add(uint256 a, uint256 b) internal pure returns (uint256) {
uint256 c = a + b;
assert(c >= a);
return c;
} }
contract DEX {
event Bought(uint256 amount);
event Sold(uint256 amount);


IERC20 public token;

constructor() public {
token = new ERC20Basic();
}

function buy() payable public {
uint256 amountTobuy = msg.value;
uint256 dexBalance = token.balanceOf(address(this));
require(amountTobuy > 0, "You need to send some Ether");
require(amountTobuy <= dexBalance, "Not enough tokens in the reserve");
token.transfer(msg.sender, amountTobuy);
emit Bought(amountTobuy);
}

function sell(uint256 amount) public {
require(amount > 0, "You need to sell at least some tokens");
uint256 allowance = token.allowance(msg.sender, address(this));
require(allowance >= amount, "Check the token allowance");
token.transferFrom(msg.sender, address(this), amount);
payable(msg.sender).transfer(amount);
emit Sold(amount);
}

receive() external payable {
buy();
}
}