Dai, USDT permit function

Support Contracts
1

Hi

I was just wondering how to use the DAI permit and compared it with ERC20Permit contract. What is the difference? I just saw that DAI contract has a permit function but with more parameters. I guess it will not work with the permit from ERC20Permit contract?

Does USDT not have a permit function?

2

Regarding DAI, you can see the section in the EIP about Backwards Compatibility.

USDT doesn't seem to have a permit function. The contract predates the development of permit and it is not upgradeable.

3

Thanks for your answer. I want to send Dai token to a contract and I wrote the following function for that. The permit function for dai is called on UI site daiToken.permit(...args);

I am thinking if this maybe not be better to add the daiToken.permit(...args); into the sendToken function before instead of permitting over the UI.

  function sendToken(
        address _token,
        address _to,
        uint256 _amountIn,
        uint256 _merchantID,
        uint256 _orderID,
        uint256 _deadline
    ) public override ensure(_deadline) {
        IERC20 token = IERC20(_token);
        require(token.balanceOf(msg.sender) > _amountIn, "Not enough balance");
        require(_amountIn > 0, "amount should be > 0");
        require(_orderID != 0, "sendToken: orderID is empty");
        require(_merchantID != 0, "sendToken: merchandID is empty");

        address _merchantUID = PaymentLibrary.merchantFor(
            factory,
            _to,
            _merchantID
        );

        uint256 _amountInMinusFee = PaymentLibrary.getAmountOut(
            _amountIn
        );

        // msg.sender is router
        token.safeTransferFrom(msg.sender, _merchantUID, _amountIn);
        uint256 _fees = _amountIn.sub(_amountInMinusFee);
        // pass amount && fees
        IMerchant(_merchantUID).mint(
            msg.sender,
            _to,
            _amountIn,
            _fees,
            _orderID
        );
    }