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I'm testing transferring a minted NFT from a regular address to this smart contract's address (I'm creating a DEX), but whenever I test it with Truffle I get the error VM Exception while processing transaction: revert.

contract Exchange is ERC721Enumerable {
    function sellToExchange(uint256 _tokenId, uint256 _sellPrice) public {
       safeTransferFrom(msg.sender, payable(this), _tokenId);
    }
}

I don't understand why I keep getting this error. If I call the exact same function with transferFrom() instead, it passes my test, but not with safeTransferFrom().

I'm using OpenZeppelin's ERC721 contract by the way.

Also, should I make the smart contract's address a type of address or address payable in order to receive the NFT?

ANSWER:

The issue was that in order to receive NFT/ERC721 tokens to a smart contract address, that address needs to inherit ERC721Holder.sol which is found on OpenZeppelin's contract GitHub repo (link below).

https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC721/utils/ERC721Holder.sol

3
  • Has msg.sender authorized the contract to access to _tokenId? See approve in their docs docs.openzeppelin.com/contracts/3.x/api/token/…
    – Ismael
    Jun 9, 2021 at 5:36
  • I figured out why. I needed to inherit ERC721Receiver to be able to let my contract accept NFT tokens.
    – Adrian D.
    Jun 9, 2021 at 22:23
  • It will be awesome if you could add the solution as an answer so it can help others.
    – Ismael
    Jun 10, 2021 at 0:39

1 Answer 1

-1

Try this: safeTransferFrom(ownerOf(_tokenId), payable(this), _tokenId);

1
  • payable address is only for receiving ether, not tokens.
    – turboza
    Jun 16 at 16:07

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