Solidity Uniswap – Optimized Swaps with swapExactTokensForTokens for Different Addresses

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I've already spent a hours to figuring out, how to do the following swap order across different exchanges/DEX using my own smart contract. In the image below (optimal Example), the swap is effectively performed. There is no intermediate step back to the origin smartcontract address and the token is passed directly to the next pool (but via another DEX).

Optimized Example:

How can this be done technically? Unfortunately I didn't manage it with swapExactTokensForTokens, at least I get an error when I want to specify address to the pool.

Here is a bad example and not optimized.

In this example, the swap is transferred back to the original smart contract and it do another swap from the contract. That is not efficient and of course costs gas!

I hope you can help me here?
Thank you very much

Best Answer

You don't have to use the Uniswap V2 router but instead you can directly interact with the pairs. Simply transfer the exact input amount to the pair and then call swap() on the pair passing the next pair as to.

You can use UniswapV2Library.getAmountsOut() to compute on-chain the correct amounts for arbitrarily long paths.

Check the code of swapExactTokensForTokens() to better understand how to perform these operations.

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Try increasing the timestamp to (datetime.now() + 60000) which is basically 1min., 250 is 250 miliseconds which could be not enough for the execution.

Solidity – Checking If Smart Contract is Secure and Optimized

The code seems to be secure but here are a couple of things you can do to improve the overall efficiency of the smart contract

Remove the hardcoded _tokenAddress value from the constructor so it would look like this

constructor(address _tokenAddress) {
        owner = msg.sender;
        token = IBEP20(_tokenAddress);
    }

Add a recipientsCount variable to store the number of recipients instead of iterating over the entire recipientsList to count them. This can make the recipientsCount function more efficient.

uint256 public recipientsCount;

function distributeTokens() public onlyOwner {
        require(token.balanceOf(address(this)) >= 1000000 * recipientsCount, "Insufficient balance to distribute tokens");

        for (uint256 i = 0; i < recipientsList.length; i++) {
            if (recipients[recipientsList[i]]) {
                require(token.transfer(recipientsList[i], 1000000), "Token transfer failed");
            }
        }

Additionally, same variable will also be used in below 2 functions from point 3.

Modify the addRecipient and removeRecipient functions to check if the recipient is already added or removed before updating the recipients mapping and recipientsCount variable to avoid unnecessary gas costs. The updated code should look like this

function addRecipient(address recipient) public onlyOwner {
        if (!recipients[recipient]) {
            recipients[recipient] = true;
            recipientsCount++;
        }
    }

    function removeRecipient(address recipient) public onlyOwner {
        if (recipients[recipient]) {
            recipients[recipient] = false;
            recipientsCount--;
        }
    }

Best Answer

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UniswapV2Router02 – How to Use swapExactTokensForTokens Deadline

Solidity – Checking If Smart Contract is Secure and Optimized

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