与 Uni V2 交互时如何修复 'TransferHelper: ETH_TRANSFER_FAILED'

Question

我正在处理 Uniswap V2 路由合约中 safeTransferETH 辅助函数的一个奇怪问题。

我正在尝试使用 Uniswap V2 路由器提供的 swapExactTokensForETH 功能将合约持有的代币交换到 Uniswap 以换取以太币。（功能代码出现在 Uniswap's github in router1 上）。被调用的函数是：

function swapExactTokensForETH(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline)
        external
        override
        ensure(deadline)
        returns (uint[] memory amounts)
    {
        require(path[path.length - 1] == WETH, 'UniswapV2Router: INVALID_PATH');
        amounts = UniswapV2Library.getAmountsOut(factory, amountIn, path);
        require(amounts[amounts.length - 1] >= amountOutMin, 'UniswapV2Router: INSUFFICIENT_OUTPUT_AMOUNT');
        TransferHelper.safeTransferFrom(path[0], msg.sender, UniswapV2Library.pairFor(factory, path[0], path[1]), amounts[0]);
        _swap(amounts, path, address(this));
        IWETH(WETH).withdraw(amounts[amounts.length - 1]);
        TransferHelper.safeTransferETH(to, amounts[amounts.length - 1]);
    }

此代码中唯一抛出错误的部分是 TransferHelper.safeTransferETH 函数，即：

function safeTransferETH(address to, uint value) internal {
    (bool success,) = to.call{value:value}(new bytes(0));
    require(success, 'TransferHelper: ETH_TRANSFER_FAILED');
}

我的代码是：

function uniV2ReceiveETH(address _token0, uint _amount0) public payable returns (uint[] memory amountsReceived) {
        require(_amount0 > 0, "Must provide tokens if we want tokens in return!");
        address[] memory path = new address[](2);
        path[0] = _token0;
        path[1] = WETH;

        IERC20 token;
        token = IERC20(_token0);

        if (token.balanceOf(address(this)) > 0) {
            _amount0 = token.balanceOf(address(this));
        }

        require(token.approve(address(uniV2Router), _amount0 + 10000), "approval failed");

        // Swap logic
        uint amountOutMin = UniswapV2Library.getAmountsOut(address(uniV2Factory), _amount0, path)[1];
        amountsReceived = uniV2Router.swapExactTokensForETH(_amount0, amountOutMin, path, address(this), deadline);
        uint endBalance = address(this).balance;

        // Let everyone know we're done!
        emit Swap(msg.sender, _amount0, endBalance);
}

其他一些注意事项是：

合约确实从其他地址接收 ETH，没有问题。
我正在使用安全帽和主网的分叉版本进行测试。
该合约还适用于 Uniswap 路由器的其他交换功能，包括 SwapExactETHForTokens 和 SwapExactTokensForTokens。

Answer 1

我通过定义 payable fallback 函数解决了这个问题：

fallback() external payable { }

在我的智能合约中。

与 Uni V2 交互时如何修复 'TransferHelper: ETH_TRANSFER_FAILED'

How to fix 'TransferHelper: ETH_TRANSFER_FAILED' when interacting with Uni V2

ethereum

solidity

smartcontracts

uniswap