How to best override private function _doSafeTransferAcceptanceCheck in ERC1155?

Support Contracts
1

Hi all,

I’m trying to inherit the ERC1155 base contract as provided by OZ. Specifically, I’m overriding safeTransferFrom. I’m trying to mimic the original implementation as closely as possible, including teh call to _doSafeTransferAcceptanceCheck, however, because that function is private, I can’t call it.

What’s the best solution to getting around this problem? I can’t override it as it’s a private function (as far as I know).

I’m between two options, though I feel like there’s probably a better one I hadn’t considered.

  1. Reimplementing the doSafeTransferAcceptanceCheck under a new name
  2. Reimplementing the entire contract and adding my functions (rather than inheriting)

I certainly want this functionality in the end so removing the function call entirely seems like a bad idea.

:computer: Environment

N/A

:memo:Details

:1234: Code to reproduce

    /**
     * @dev See {IERC1155-safeTransferFrom}.
     */
    function safeTransferFrom(
        address from,
        address to,
        uint256 id,
        uint256 amount,
        bytes memory data
    ) public virtual override {
        require(to != address(0), "ERC1155: transfer to the zero address");
        require(
            from == _msgSender() ||
                isApprovedForAll(from, _msgSender())
            "ERC1155: caller is not owner, token holder, or pod manager"
        );

        // Imagine some unique implementation here

        address operator = _msgSender();

        _balances[id][from] = _balances[id][from].sub(
            amount,
            "ERC1155: insufficient balance for transfer"
        );
        _balances[id][to] = _balances[id][to].add(amount);

        emit TransferSingle(operator, from, to, id, amount);

        _doSafeTransferAcceptanceCheck(operator, from, to, id, amount, data);
    }

    function _doSafeTransferAcceptanceCheck(
        address operator,
        address from,
        address to,
        uint256 id,
        uint256 amount,
        bytes memory data
    ) private override {
        if (to.isContract()) {
            try
                IERC1155Receiver(to).onERC1155Received(
                    operator,
                    from,
                    id,
                    amount,
                    data
                )
            returns (bytes4 response) {
                if (
                    response != IERC1155Receiver(to).onERC1155Received.selector
                ) {
                    revert("ERC1155: ERC1155Receiver rejected tokens");
                }
            } catch Error(string memory reason) {
                revert(reason);
            } catch {
                revert("ERC1155: transfer to non ERC1155Receiver implementer");
            }
        }
    }
1 Like
2

Just like what you said above, _doSafeTransferAcceptanceCheck is a private function, so you can not rewrite it, what you can do is to rewrite the function safeTransferFrom, so then you can do whatever you want to do.

1 Like
3

Hi @willKim19,

You could look at using the hook _beforeTokenTransfer, see Using Hooks. If you can’t do what you want to do using hooks, then you should do as @Skyge recommended.

4

Found this topic while trying to override the 1155 transfer function as well and ran into the same problem

The hooks solution works, but it took me a while to figure out so maybe this will help someone else too:

Here’s my working code

 function safeTransferFrom(
          address from,
          address to,
          uint256 id,
          uint256 amount,
          bytes memory data
      )
          public
          virtual
          override
      {
          //Fractal Requirements
          if(tokenIdToShares[id] > 0){
            //this is an NFT, require all the shares are locked
            require(
              (lockedToTotal[id][to] == 10000),
                "ERC1155: caller has not transferLocked this many shares to this transfer."
            );
            }
          else{
            //these are shares
            //Owner must have this many shares, and they much be unlocked.
            require(
              (getPercentByNFT(msg.sender, id) - lockedShares[msg.sender][id] >= amount),
                "Fraktal ERC1155: caller does not have this many unlocked shares."
            );
          }
           //call the original function that you wanted.
          super.safeTransferFrom(
             from,
             to,
             id,
             amount,
             data
          );
           //do some other stuff
        }

I added some of my own requirements at the top of the function, which is what I wanted changed. But _balances is private, and a few other functions were private so it didnt compile. To fix I did 2 things, after reading the Hooks explanation as linked above.

  1. make my function virtual
  2. Do the things you want differently, and then call the existing safeTransferFrom function as a super so all the good stuff happens: