IUniswapV2Router02. smart在smart合同中失败

Question

我试图通过uniswap路由器合同将weth令牌交换为dai令牌(都是ERC20)：

我尝试了两种方法：

1.使用松露控制台操纵weth/dai/路由器合同。这种方法效果很好。详情见下文：

// Dai.sol
pragma solidity ^0.6.6;


contract Dai {
    function balanceOf(address owner) external view returns(uint) {}
    function totalSupply() external view returns (uint256){}
    function transfer(address recipient, uint256 amount) external returns (bool){}
    function allowance(address owner, address spender) external view returns (uint256){}
    function approve(address spender, uint256 amount) external returns (bool){}
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool){}
}

// Weth.sol
pragma solidity ^0.6.6;

contract Weth {
    function deposit() public payable {}
    function approve(address spender, uint amount) external {}
    function allowance(address owner, address spender) external view returns(uint) {}
    function balanceOf(address owner) external view returns(uint) {}
    function transfer(address recipient, uint256 amount) external returns (bool){}
}

// Router.sol

pragma solidity ^0.6.6;

contract Router {
    function swapExactTokensForTokens(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline ) external returns (uint[] memory amounts){}
    function getAmountsOut(uint amountIn, address[] memory path) public view returns (uint[] memory amounts){}
    function getAmountsIn(uint amountOut, address[] memory path)public view virtual returns (uint[] memory amounts) {}
}

松露控制台上有一步一步的命令行：

truffle(kovan)> dai = await Dai.at("0x4f96fe3b7a6cf9725f59d353f723c1bdb64ca6aa")
truffle(kovan)> weth = await Weth.at("0xd0a1e359811322d97991e03f863a0c30c2cf029c")
truffle(kovan)> router =await Router.at("0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D")

truffle(kovan)> amountIn = await router.getAmountsIn(web3.utils.toWei("1"), [weth.address, dai.address])
truffle(kovan)> amountIn = amountIn[0]
truffle(kovan)> amountOut = web3.utils.toWei("1")
truffle(kovan)> weth.approve(router.address, amountIn)
truffle(kovan)> time = Math.floor((Date.now()/1000)) + 60*120
truffle(kovan)> router.swapExactTokensForTokens(amountIn, amountOut, [weth.address, dai.address], accounts[0], time)

在这种情况下，swapExactTokensForTokens的事务已经成功通过(https://kovan.etherscan.io/tx/0x11e51ad94d90ec9b2182768bcea87ad5a15d5cf83a91a02d52f2990cbaed5c61)。

1. 从uniswapv2导入IUniswapV2Router02.sol，并在我的合同中操作router.swapExactTokensForTokens。

// SwapToken.sol
pragma solidity ^0.6.6;

import "@uniswap/v2-periphery/contracts/interfaces/IUniswapV2Router02.sol";
import "@uniswap/v2-core/contracts/interfaces/IERC20.sol";

contract SwapTokens {
    
    IUniswapV2Router02 public uniRouter = IUniswapV2Router02(0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D);
    
    event test (uint timestamp, uint amountIn, uint amountOut, address[] path, uint allowance, address sender);
    
    function swapper(address token1, address token2) public  {
        address[] memory path = new address[](2);
        path[0] = token1;
        path[1] = token2;
        uint amountOut = 1 ether;
        uint amountIn = uniRouter.getAmountsIn(
            amountOut,
            path
        )[0];
                
        IERC20(token1).approve(address(uniRouter), amountIn);
        
        uint allowed = IERC20(token1).allowance(msg.sender, address(uniRouter));        
        
        emit test(now+90, amountIn, amountOut, path, allowed, msg.sender);

        uniRouter.swapExactTokensForTokens(
            amountIn, 
            amountOut,
            path, 
            msg.sender, 
            now + 120
        );
    }
}

然后运行swapper函数，如下所示：

sw = await SwapTokens.deployed()
sw.swapper(weth.address, dai.address)

事务失败，错误为“TransferHelper:TRANSFER_FROM_FAILED”(https://kovan.etherscan.io/tx/0x3324fd65004e001163b665b79583f894e17854bc3371b89f39d472504cb4b46a)

这两种方式对我来说都是一样的。我不知道我做错了哪一部分。

Answer 1

当您从合同内部调用uniswap合同时，msg.sender将始终是您的合同，因为您正在进行外部操作，请确保

1. 您的合同要么有您想要交换的令牌，要么有津贴。
2. 检查您是否在正确的网络上并使用正确的地址