What's the interfaceID for ERC-20?

Question

What's the interfaceID for ERC-20? It's not in the EIP. It's shown for 165 and 721 but not for ERC-20.

Answer 1

Short Answer probably 0x36372b07

I think you can add the interfaces like this in your ERC20 Contract constructor, you need to import IERC20 and ERC20 and ERC165 (or ERC165Storage) from OpenZeppelin

_registerInterface(type(IERC20).interfaceId);
_registerInterface(ERC20.name.selector);
_registerInterface(ERC20.symbol.selector);
_registerInterface(ERC20.decimals.selector);

and test them like this

const erc165Interface = await mytokenInstance.supportsInterface('0x01ffc9a7'); // true
const tokenInterface = await mytokenInstance.supportsInterface('0x36372b07'); // true
const tokenNameInterface = await mytokenInstance.supportsInterface('0x06fdde03'); // true
const tokenSymbolInterface = await mytokenInstance.supportsInterface('0x95d89b41'); // true
const tokenDecimalsInterface = await mytokenInstance.supportsInterface('0x313ce567'); // true
const tokenNoneExistingInterface = await mytokenInstance.supportsInterface('0x19be5360'); // false

Answer 2

Solidity has type function:

function interfaceId() public pure returns(bytes4){
    return type(IERC20).interfaceId;
}

with this function, you can get the interfaceId of any interface

Answer 3

Found this example in a contract.

/**
* @dev See {IERC165-supportsInterface}
*/
function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
       return
           interfaceId == type(IERC721).interfaceId ||
           interfaceId == type(IERC721Metadata).interfaceId ||
           super.supportsInterface(interfaceId);
}

Hope it helps!