NFT Token Standards (ERC-721/1155) 3

Question 1

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

Accepted Answer

Transfer

Answer

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

Question 2

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

Accepted Answer

The amount of a specific token id the account holds

Answer

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

Question 3

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

Accepted Answer

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

Answer

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

Question 4

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

Accepted Answer

Batch operations and shared metadata reduce per-token overhead

Answer

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

Question 5

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

Accepted Answer

onERC1155Received

Answer

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

NFT Development Practice Test