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how to I write timestamp in erc721-contract when someone transfer it

I want to know when the current owner has this token by storing a new timestamp every time an erc721 token is traded. I want to store a timestamp (ex. string timestamp = "20220430") in my contract whenever transferFrom and safeTransferFrom are executed, please give me an idea of the best way. My contract inherits from ERC721A(AZUKI standard).

Solution

  • My suggestion is to add an event:

    event TransferTimestamp(uint256 tokenId, address from, address to, uint256 timestamp);

    And emit it on either of the two methods, using block.timestamp to get the timestamp:

    emit TransferTimestamp(tokenId, msg.sender, to, block.timestamp);

    Note: block.timestamp is inaccurate. Miners are directly able to influence its value with no checks.

    Alternatively, you could use the built-in Transfer event present in all EIP-721 NFTs. The event list has the block when it was emitted, which can then be converted to a timestamp in the DApp's frontend.