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I wrote code to buy DAI using ETH on Uniswap V2 as follows:

function buyCryptoOnUniswap(uint256 etherCost , address cryptoToken) public payable returns(uint256){
//address cryptoToken = 0x4F96Fe3b7A6Cf9725f59d353F723c1bDb64CA6Aa;

require(etherCost <= address(this).balance , "Insufficient funds")



    uint256 cryptoAmountPurchasable = estimateTokensThatETHCanBuy(etherCost , cryptoToken)[1];
    cryptoAmountPurchasable = cryptoAmountPurchasable.mul(11).div(10);// multiply by 1.1
 
    uint deadline = now + 300; // using 'now' for convenience, for mainnet pass deadline from frontend!

   
    usi.swapExactETHForTokens.value(etherCost)(0, getPathForETHToToken(cryptoToken), address(this), deadline);

   return cryptoAmountPurchasable;

}

 function estimateTokensThatETHCanBuy(uint ethAmount , address crypto) public view returns (uint[] memory) {
       return usi.getAmountsOut(ethAmount, getPathForETHToToken(crypto));
  }

  function getPathForETHToToken(address crypto) private view returns (address[] memory) {
    address[] memory path = new address[](2);
    path[0] = usi.WETH();
    path[1] = crypto;
    
    return path;
  }

The code works but I was expecting an exchange rate of about 180 -> 230 but to my dismay, 0.1 ETH only gave me 1.926 DAI and 1 ETH gave me about 19.26 DAI also.

Here is the transaction using 0.1ETH.

I am using the DAI token for kovan: 0x4F96Fe3b7A6Cf9725f59d353F723c1bDb64CA6Aa.

Is something wrong with my code?

Please help.

UPDATE

I wrote code to buy DAI on Kyber and I got it at the expected rate range:

See the transaction here.

  • Take a good look at .mul(11).div(10);// divide by 1.1 – goodvibration Jul 2 at 12:11
  • Hmm, true that...should be multiply by 1.1. Thanks. But it would still be off by a factor of at least 10, though – gbenroscience Jul 2 at 12:14
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This is because you're doing this on Kovan. The DAI/WETH uniswap pool on Kovan obviously doesn't use real (with value) DAI or WETH, so there is no arbitrage to push it to the market rate of ETH/DAI. See the pool here and look at the token amounts, ~660 kWETH and ~25,000 kDAI which gives a rate of ~38 DAI per ETH. The price has gone up since your test transaction, but it's just due to the testnet using valueless tokens

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