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

Recall & Review

beginner

What is ERC-721 in blockchain?

ERC-721 is a standard for creating Non-Fungible Tokens (NFTs) on the Ethereum blockchain. Each token is unique and cannot be replaced by another.

beginner

What function in ERC-721 returns the owner of a specific token?

The function ownerOf(tokenId) returns the address of the owner of the token with the given tokenId.

intermediate

Why does ERC-721 require a transferFrom function?

The transferFrom function allows the owner or an approved address to transfer ownership of a token to another address, enabling token trading and movement.

intermediate

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

The approve function lets the token owner authorize another address to transfer a specific token on their behalf.

intermediate

Name two events defined in the ERC-721 standard and their purpose.

1. Transfer: Emitted when ownership of a token changes.<br>2. Approval: Emitted when a token owner approves another address to manage a token.

Which function in ERC-721 returns the total number of tokens owned by an address?

A ownerOf

B balanceOf

C totalSupply

D tokenURI

The balanceOf function returns how many tokens an address owns.

What does the tokenURI function provide in an ERC-721 contract?

A The owner address of a token

B The total number of tokens

C The metadata URL for a token

D The approval status of a token

The tokenURI function returns a URL pointing to metadata describing the token.

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

A Transfer

B TokenMoved

C OwnershipChanged

D Approval

The Transfer event signals that a token's ownership has changed.

What is the main difference between ERC-20 and ERC-721 tokens?

A ERC-20 tokens are only for Ethereum, ERC-721 tokens are for Bitcoin

B ERC-20 tokens are unique, ERC-721 tokens are fungible

C ERC-20 tokens cannot be transferred, ERC-721 tokens can

D ERC-20 tokens are fungible, ERC-721 tokens are unique

ERC-20 tokens are fungible (all tokens are the same), while ERC-721 tokens are unique and non-fungible.

Which function allows an approved address to transfer a token on behalf of the owner?

A transferFrom

B safeTransferFrom

C approve

D setApprovalForAll

The transferFrom function lets an approved address transfer a token.

Explain the key functions and events that an ERC-721 contract must implement.

Think about how tokens are owned, transferred, and approved.

Describe how ERC-721 tokens differ from ERC-20 tokens and why this matters.

Consider what makes each token type special and their typical uses.