How to use SafeERC20 with interfaces

Smart Contracts
1

I know for SafeERC20 you just add

using SafeERC20 for IERC20;

However, if I want to define interfaces, what would the syntax be? I currently have it as

interface ERC20Interface {
  function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
  function balanceOf(address account) external returns (uint256);
}

contract Test is ERC721Pausable
{
  using SafeERC20 for ERC20Interface;
}

For some reason, when I call safeTransferFrom it says it's not found

2

The SafeERC20 functions are defined to work on IERC20, so safeTransferFrom(IERC20 token, ...). You can't change that with the using for statement.

3

Hey, is it possible to do it for an interface inheriting from IERC20 then? For example, in the following code, got this error" TypeError: Member "safeTransfer" not found or not visible after ... lookup...".

// SPDX-License-Identifier: MIT

pragma solidity 0.8.17;

import "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import "@openzeppelin/contracts/token/ERC20/ERC20.sol";

interface IToken is IERC20 {}

contract TestToken is IToken, ERC20("Test Token", "TT") {}

contract Test {
    using SafeERC20 for IERC20;

    IToken public token;

    constructor (address _tokenAddr) {
        token = IToken(_tokenAddr);
    }

    function doSth() external {
        token.safeTransfer(msg.sender, 1 ether);
    }
}
4

I believe Solidity doesn't allow this. It needs to be the exact type. So you should write IERC20(token).safeTransfer(...)

1 Like
5

Thanks, that's what I figured.