NFT Advanced NFT Mechanics 3

Question 1

What does setApprovalForAll allow in an ERC-721 contract?

Accepted Answer

Approve an operator for all of an owner's tokens

Answer

setApprovalForAll grants or revokes an operator permission over every token an owner holds in that contract.

Question 2

Why might a developer use OpenZeppelin's ERC721Enumerable extension?

Accepted Answer

To enable on-chain enumeration of all tokens and per-owner tokens

Answer

ERC721Enumerable adds totalSupply and indexing functions so tokens can be enumerated on-chain.

Question 3

What is a reentrancy risk when handling NFT purchases with ETH refunds?

Accepted Answer

An external call letting an attacker re-enter before state updates

Answer

An external call before updating state can let a malicious receiver re-enter and exploit stale balances.

Question 4

Which pattern is recommended to prevent reentrancy in withdrawal functions?

Accepted Answer

Update state before external calls

Answer

Following checks-effects-interactions—updating state before the external call—prevents reentrant exploitation.

Question 5

What does a minimal proxy (ERC-1167) clone primarily save on?

Accepted Answer

Deployment gas costs

Answer

ERC-1167 clones delegate to a single implementation, drastically reducing per-deployment gas.

NFT Development Practice Test