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Token Standards (ERC-721/1155) Flashcards

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Read the first 7 Token Standards (ERC-721/1155) flashcards as text

  1. Which event must ERC-721 emit when a token changes hands?

    Answer: Transfer

    ERC-721 emits Transfer(from, to, tokenId) on every mint, burn, and transfer.

  2. In ERC-1155, what does balanceOf(account, id) return?

    Answer: The amount of a specific token id the account holds

    ERC-1155 balanceOf takes both an account and an id, returning that account's holding of that id.

  3. What is the purpose of setApprovalForAll in both ERC-721 and ERC-1155?

    Answer: Grant an operator control over all of the owner's tokens

    setApprovalForAll authorizes an operator to manage every token the owner holds in that contract.

  4. Why is ERC-1155 generally more gas-efficient for large drops than ERC-721?

    Answer: Batch operations and shared metadata reduce per-token overhead

    Batch transfers and a shared id-based URI cut redundant transactions and storage writes.

  5. Which callback must a contract implement to safely receive an ERC-1155 single transfer?

    Answer: onERC1155Received

    onERC1155Received must return its magic value so the transfer to a contract succeeds.

  6. In OpenZeppelin's ERC-721, what does _mint(to, tokenId) require about the tokenId?

    Answer: It must not already be owned

    _mint reverts if the tokenId already exists, preventing duplicate ownership.

  7. What does ERC-2981 add on top of ERC-721/1155?

    Answer: A standardized royalty info interface

    ERC-2981 provides royaltyInfo so marketplaces can query a standard royalty amount.