There're 2 future NFT collections.

Is it possible to create the contracts for them in such a way that whenever an NFT of collection_1 c1 gets, some NFTs from collection_2 c2 of the same account get transfered automatically to the receiver as well?

Meaning, even when a user decides to send an NFT from c1 from his wallet manually, without calling a special function myTransferNFTOf2Collections(...) which I may create. In other words, it should occur in all possible cases, without any additional effort from the user.

option #1:

the contract for collection_1 has been created in the past, and therefore can't be changed now. Would this be possible still?

1 Answer 1


It is possible to create NFTs bound to other NFTs. Let's say you have an original collection A and a "mirrored" collection B.

By borrowing the ownerOf function from A, we can make one in B like this:

function ownerOf(
    uint256 tokenId
) public view virtual override returns (address) {
    return IERC721(originalCollection).ownerOf(tokenId);

you've effectively bound all new NFTs to the owners of the original collection. This is how Cyberkongz have "airdropped" a copy of the original version with on-chain metadata to every holder. When an original is transferred, the internal mapping update happens in one smart-contract, but it is reflected in both. You don't have to use any expensive storage at all which makes it very cheap to deploy.

Note that you may have to fire a specific "batch mint" event when the new contract is deployed in order for off-chain indexers to display the NFTs in user wallets. You can read more about it in a blog by 0xInuarashi.

  • I don't understand. Where will function ownerOf(...) have to be placed?
    – Nondi
    Jun 8, 2023 at 19:34
  • The ownerOf function is part of the IERC721 standard, every NFT smart-contract needs to have it. Dive deeper into the implementation on OpenZeppelin's GitHub and it will all make more sense.
    – Ape Toshi
    Jun 8, 2023 at 19:48
  • That's not what I asked about
    – Nondi
    Jun 8, 2023 at 21:10
  • I've asked about 1-n rather than 1-1
    – Nondi
    Jun 8, 2023 at 23:49

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