Uniswap: swapExactETHForTokens (3 addresses in path[])

Ivan_Perroud · September 1, 2020, 6:29pm

Hello!

as exercise for this course 101, I have integrated the Uniswap V2 router to program a swap. It is successful if I swap ETH to DAI, but

Once I want to add a path along the route to trade ETH to USDC via DAI for example, it does note work.

Instead of showing the code, I show what my code exactly calls, see in the image below. I get the same problem in my code, as well as in the etherscan GUI:

does anyone know how to do such a swap correctly ?
Thanks,
Ivan

smileBTC · September 2, 2020, 8:54am

Hi Ivan,

do you get a UniswapV2 error code? If yes,

github.com

Uniswap/uniswap-v2-periphery/blob/master/contracts/UniswapV2Router02.sol

pragma solidity =0.6.6;

import '@uniswap/v2-core/contracts/interfaces/IUniswapV2Factory.sol';
import '@uniswap/lib/contracts/libraries/TransferHelper.sol';

import './interfaces/IUniswapV2Router02.sol';
import './libraries/UniswapV2Library.sol';
import './libraries/SafeMath.sol';
import './interfaces/IERC20.sol';
import './interfaces/IWETH.sol';

contract UniswapV2Router02 is IUniswapV2Router02 {
    using SafeMath for uint;

    address public immutable override factory;
    address public immutable override WETH;

    modifier ensure(uint deadline) {
        require(deadline >= block.timestamp, 'UniswapV2Router: EXPIRED');
        _;

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and

github.com

Uniswap/uniswap-v2-core/blob/1f563ce23b6dbe972d667c79058d0299e6f10ff6/contracts/UniswapV2Pair.sol

pragma solidity =0.5.16;

import './interfaces/IUniswapV2Pair.sol';
import './UniswapV2ERC20.sol';
import './libraries/Math.sol';
import './libraries/UQ112x112.sol';
import './interfaces/IERC20.sol';
import './interfaces/IUniswapV2Factory.sol';
import './interfaces/IUniswapV2Callee.sol';

contract UniswapV2Pair is IUniswapV2Pair, UniswapV2ERC20 {
    using SafeMath  for uint;
    using UQ112x112 for uint224;

    uint public constant MINIMUM_LIQUIDITY = 10**3;
    bytes4 private constant SELECTOR = bytes4(keccak256(bytes('transfer(address,uint256)')));

    address public factory;
    address public token0;
    address public token1;

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might help to pinpoint the problem.

Best,
Philipp