ERC-721 Non-Fungible Token Standard
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What is a Non-Fungible Token?
A Non-Fungible Token (NFT) is used to identify something or someone in a unique way. This type of Token is perfect to be used on platforms that offer collectible items, access keys, lottery tickets, numbered seats for concerts and sports matches, etc. This special type of Token has amazing possibilities so it deserves a proper Standard, the ERC-721 came to solve that!
What is ERC-721?
The ERC-721 introduces a standard for NFT, in other words, this type of Token is unique and can have different value than another Token from the same Smart Contract, maybe due to its age, rarity or even something else like its visual. Wait, visual?
Yes! All NFTs have a
uint256 variable called
tokenId, so for any ERC-721 Contract, the pair
contract address, uint256 tokenId must be globally unique. That said, a dapp can have a "converter" that
tokenId as input and outputs an image of something cool, like zombies, weapons, skills or amazing kitties!
The ERC-721 (Ethereum Request for Comments 721), proposed by William Entriken, Dieter Shirley, Jacob Evans, Nastassia Sachs in January 2018, is a Non-Fungible Token Standard that implements an API for tokens within Smart Contracts.
It provides functionalities like to transfer tokens from one account to another, to get the current token balance of an account, to get the owner of a specific token and also the total supply of the token available on the network. Besides these it also has some other functionalities like to approve that an amount of token from an account can be moved by a third party account.
If a Smart Contract implements the following methods and events it can be called an ERC-721 Non-Fungible Token Contract and, once deployed, it will be responsible to keep track of the created tokens on Ethereum.
1 function balanceOf(address _owner) external view returns (uint256);2 function ownerOf(uint256 _tokenId) external view returns (address);3 function safeTransferFrom(address _from, address _to, uint256 _tokenId, bytes data) external payable;4 function safeTransferFrom(address _from, address _to, uint256 _tokenId) external payable;5 function transferFrom(address _from, address _to, uint256 _tokenId) external payable;6 function approve(address _approved, uint256 _tokenId) external payable;7 function setApprovalForAll(address _operator, bool _approved) external;8 function getApproved(uint256 _tokenId) external view returns (address);9 function isApprovedForAll(address _owner, address _operator) external view returns (bool);10அனைத்தையும் காட்டு