ERC-721 NFT standard in Blockchain / Solidity - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the ERC-721 standard?

ERC-721 is a standard for creating Non-Fungible Tokens (NFTs) on the Ethereum blockchain. It defines how unique digital assets can be owned and transferred.

beginner

What makes ERC-721 tokens different from ERC-20 tokens?

ERC-721 tokens are unique and non-fungible, meaning each token is different and cannot be exchanged one-to-one. ERC-20 tokens are fungible and identical to each other.

intermediate

Name two key functions defined in the ERC-721 standard.

Two key functions are ownerOf(tokenId) which returns the owner of a specific token, and transferFrom(from, to, tokenId) which transfers ownership of a token.

intermediate

What is the purpose of the tokenURI function in ERC-721?

tokenURI(tokenId) returns a URL pointing to metadata about the token, such as images or descriptions, helping wallets and apps display the NFT properly.

intermediate

Why is the Approval event important in ERC-721?

The Approval event signals that the owner has allowed another address to manage a specific token, enabling marketplaces or other contracts to transfer tokens on behalf of the owner.

Which of the following best describes an ERC-721 token?

A A decentralized exchange protocol

B A fungible token like a cryptocurrency

C A smart contract programming language

D A unique digital asset on Ethereum

ERC-721 tokens represent unique digital assets, unlike fungible tokens.

What does the ownerOf(tokenId) function return?

A The metadata URL of the token

B The owner address of the token with the given ID

C The total supply of tokens

D The balance of tokens owned by an address

ownerOf returns the address that owns a specific token.

Which event is emitted when a token is transferred in ERC-721?

A Approval

B Mint

C Transfer

D Burn

The Transfer event is emitted whenever a token changes ownership.

What is the main purpose of the tokenURI function?

A To provide metadata about the token

B To transfer the token

C To approve another address

D To check token balance

tokenURI returns a link to the token's metadata like images or descriptions.

Which of these is NOT a feature of ERC-721 tokens?

A Tokens are interchangeable one-to-one

B Each token is unique

C Supports ownership transfer

D Includes metadata support

ERC-721 tokens are non-fungible, so they are not interchangeable one-to-one.

Explain what ERC-721 tokens are and how they differ from ERC-20 tokens.

Think about how each token is special or identical.

Describe the role of the transferFrom function and the Approval event in ERC-721.

Consider how tokens move and how others get permission.