Contract standard for accepting any ERC20 (or ERC721?) as payment

[abcoathup]

@bugduino was asking how to accept ERC20 as payment in a single transaction.

Approve and transferFrom in the same tx

Hi, I’m trying to write a simple function for a contract which is supposed to approve and transferFrom msg.sender some ERC20 tokens in the contract itself, in a single tx. Ideally (this code is NOT working) I would do: function testFoo(address _token, uint256 _amount) public { // get a handle for the ERC20 contract IERC20 underlying = IERC20(_token); // approve the transfer to this contract underlying.approve(address(this), _amount); // transfer to this contract underlying.transfe…