為代幣錯誤交換確切代幣

Question

一段時間以來，我一直在嘗試通過 uniswap 進行 Swap ExactTokenforToken 交換。 不斷提出問題。

我確實有一個成功部署的合約，但它不斷收到傳輸錯誤。 通過查看文檔、帖子、此論壇等，我的理解是我沒有轉移/批准事件。

這是已部署但無法交換的代碼，以供參考：

pragma solidity 0.7.1;

import "https://github.com/Uniswap/uniswap-v2-periphery/blob/master/contracts/interfaces/IUniswapV2Router02.sol";

contract UniswapExample {
  address internal constant UNISWAP_ROUTER_ADDRESS = 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D ;

  IUniswapV2Router02 public uniswapRouter;
  address private multiDaiKovan = 0x4F96Fe3b7A6Cf9725f59d353F723c1bDb64CA6Aa;
  address private USDC = 0x2F375e94FC336Cdec2Dc0cCB5277FE59CBf1cAe5;
  
  constructor() {
    uniswapRouter = IUniswapV2Router02(UNISWAP_ROUTER_ADDRESS);
  }
  
  function convertUSDCtoEthtoDai(uint daiAmount, uint USDCAmount) public payable {
    uint deadline = block.timestamp + 15; // using 'now' for convenience, for mainnet pass deadline from frontend!
    uniswapRouter.swapExactTokensForTokens(USDCAmount, daiAmount, getPathForETHtoDAI(), address(this), deadline);
    // refund leftover ETH to user
    (bool success,) = msg.sender.call{ value: address(this).balance }("");
    require(success, "refund failed");

  }
  
  
  function getEstimatedETHforDAI(uint daiAmount) public view returns (uint[] memory) {
    return uniswapRouter.getAmountsIn(daiAmount, getPathForETHtoDAI());
  }

  function getPathForETHtoDAI() private view returns (address[] memory) {
    address[] memory path = new address[](3);
    path[0] = USDC;
    path[1] = uniswapRouter.WETH();
    path[2] = multiDaiKovan;
    
    return path;
  }
 
  
  // important to receive ETH
  receive() payable external {}
}

因此，我按照自己的方式編寫了以下代碼，但是，在“.transferFrom”上出現錯誤，提示“TypeError: Member “transferFrom” not found or not visible after argument-dependent lookup in address.”

on.approve 也是如此。 我已經為 Router02 和 IERC20 導入了 IERC20 接口。 所以我無法部署合同來測試我是否接近。

這是新代碼：

import "https://github.com/Uniswap/uniswap-v2-periphery/blob/master/contracts/interfaces/IUniswapV2Router02.sol";
import "https://github.com/Uniswap/uniswap-v2-periphery/blob/master/contracts/interfaces/IERC20.sol";

contract UniswapExample2 {

    address internal constant UNISWAP_ROUTER_ADDRESS = 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D ;

    IUniswapV2Router02 public uniswapRouter;
    address private multiDaiKovan = 0x4F96Fe3b7A6Cf9725f59d353F723c1bDb64CA6Aa;
    address private USDC = 0x2F375e94FC336Cdec2Dc0cCB5277FE59CBf1cAe5;
  
    constructor() {
     uniswapRouter = IUniswapV2Router02(UNISWAP_ROUTER_ADDRESS);
  }
    function swapTokenForETH(uint amountIn, uint amountOutMin, uint deadline) public payable returns(uint[] memory) {
        // transfer
        require(USDC.transferFrom(msg.sender, address(this), amountIn), 'transferFrom failed.');
        // approve
        require(USDC.approve(UNISWAP_ROUTER_ADDRESS, amountIn), 'approve failed.');
        // swap
        return uniswapRouter.swapExactTokensForTokens(amountIn, amountOutMin, getPathForETHtoDAI(), msg.sender, deadline);
    }
    
    
    function getPathForETHtoDAI() private view returns (address[] memory) {
    address[] memory path = new address[](3);
    path[0] = USDC;
    path[1] = uniswapRouter.WETH();
    path[2] = multiDaiKovan;
    
    return path;
  }
}

我也嘗試在實際合同中復制這些功能，但隨后我收到一個錯誤，提示必須將整個合同標記為抽象。

任何建議/指導將不勝感激！

Answer 1

您正在嘗試對address類型（未定義）執行transferFrom() function。

<address>.transferFrom()

它需要位於定義transferFrom() function 的接口上。

interface IERC20 {
    function transferFrom(address _from, address _to, uint256 _amount) external returns (bool);
}

contract UniswapExample2 {
    IERC20 private USDC = IERC20(0x2F375e94FC336Cdec2Dc0cCB5277FE59CBf1cAe5);

    function swapTokenForETH() public {
        USDC.transferFrom();
    }
}

注意：您已經（正確地）使用IUniswapV2Router02接口、 uniswapRouter屬性和方法swapExactTokensForTokens() ) 做同樣的事情。