I'm a beginner and for the past few days I have tried to recreate this tutorial: https://www.youtube.com/watch?v=a5at-FEyITQ
At first I tried to implement it on PancakeSwap, but got a Transaction Error, so after not finding a solution I returned to Uniswap.
I went on Uniswap (https://app.uniswap.org/#/swap), connected with my Metamask Account running on Ropsten test network and swapped some ETH for UNI... It worked. I looked At the Transaction and used WETH an UNI addresses bellow...
As before on Bscscan Testnet, now on Ropsten Etherscan I tried to execute function 14. swapExactTokensForTokens on UniswapV2Router (https://ropsten.etherscan.io/address/0x7a250d5630b4cf539739df2c5dacb4c659f2488d#writeContract) as shown in Image 1. As soon as I clicked write I saw on Metamask: "Transaction Error. Exception thrown in contract code.", Gas price (GWEI): 185 and amount + gass fee was only equal to gas fee. And result was as shown on Image 1, with Transaction Status: Status: Fail with error 'TransferHelper: TRANSFER_FROM_FAILED' (https://ropsten.etherscan.io/tx/0x5a1caf70fa0ae3e7a74bd80f6fad1faeb5b0185426b27eb012176e15deb5931d).
Image 1:
I used the same input fields on function 10. swapExactETHForTokens and it SUCCEEDED!
So I decided to use this function in code as shown below:
const ethers = require('ethers');
const addresses = {
WETH: '0xc778417e063141139fce010982780140aa0cd5ab',
factory: '0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f',
router: '0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D',
recipient: '0x483A7239dB71fc99a630E6C71dB2508A4dE64508'
}
const mnemonic = 'MY_MNEMONIC_KEY';
const provider = new ethers.providers.WebSocketProvider('wss://ropsten.infura.io/ws/v3/INFRA_NUMBER');
const wallet = ethers.Wallet.fromMnemonic(mnemonic);
const account = wallet.connect(provider);
const router = new ethers.Contract(
addresses.router,
[
'function getAmountsOut(uint amountIn, address[] memory path) public view returns (uint[] memory amounts)',
'function swapExactTokensForTokens(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline) external returns (uint[] memory amounts)',
'function swapExactETHForTokens(uint amountIn, uint amountOutMin, address[] calldata path, address to, uint deadline) external returns (uint[] memory amounts)'
],
account
);
async function LOL(){
const ethAmount = ethers.utils.parseEther("0.1");
//const tx = await router.swapExactTokensForTokens(
const tx = await router.swapExactETHForTokens(
ethAmount,
0,
['0xc778417e063141139fce010982780140aa0cd5ab', '0x1f9840a85d5af5bf1d1762f925bdaddc4201f984'],
addresses.recipient,
Date.now() + 1000 * 60 * 10, //10 minutes,
{
'gasLimit': 300000,
'gasPrice': ethers.utils.parseUnits('185', 'gwei'),
}
);
console.log("https://ropsten.etherscan.io/tx/" + tx.hash);
const receipt = await tx.wait();
console.log('Transaction receipt');
console.log(receipt);
}
LOL();
The result was a FAILURE as seen below:
https://ropsten.etherscan.io/tx/0xa18d2df70f04366a7ed74144d91669c37b3be02a0a57ad3a8e81c2da82806ef9
Any help/input would be much appreciated, as I have been stuck on this for a while now...
