How bad is it to change a function inside ERC721 interface?

Question

I'm creating a NFT and I want the transferFrom function to be payable. In order to do so I need to edit the ERC721 interface and make that function payable also there.

If I do so everything compiles smoothly, but my question is:
- Will other platforms don't accept my token as a standard ERC721 token? How do other platforms (eg. wallets as Trust Wallet) recognize that my token is a standard ERC721?
- Is there a better way to do this without editing the ERC721 interface? There is this discussion but no real solution: https://github.com/OpenZeppelin/openzeppelin-contracts/issues/1015

Answer 1

Actually, transferFrom is payable in EIP 721.

From https://eips.ethereum.org/EIPS/eip-721:

function transferFrom(address _from, address _to, uint256 _tokenId) external payable;

So it's not a modification at all. It's already part of the interface.

If the code you're using doesn't have payable there, you can simply add it.

Answer 2

In short: yes it's bad.

If you wish your contract to be recognized (and used) as an ERC721 contract you have to implement the correct interface (correctly).

If your contract is not ERC721 standard compliant exchanges will most likely not accept it as it would require extra coding from their part just to get your token to work. The point of standards is that everyone uses the same logic and third parties (such as exchanges) need to implement functionality only once and they can be sure that the same functionality works for all standard tokens.

Here's some more info and ideas what you could do (it's about ERC20 but it's the same idea):Can we modify ERC20 functions?

EDIT

As noted by others the transferFrom is already payable so in your case you wouldn't be breaking the standard (you'd be actually implementing it more correctly).