about.md

NFT Basics

Pseudo-code for an NFT contract that:

• Allows "minting" (creation of a token)
• Allows "transfer" (moving token from wallet A to B)
• Allows querying the "current owner of a token"
• Allows querying the "metadata" of a token (often just a IPFS hash which points to media + info)

This example is meant to illustrate some of the core concepts behind ERC 721, which is the basis for most NFTs we trade today.

Metadata

Usually the metadata is a single hash string such as 13ZcYQ53Fh9ESxbiuE827QkvikG6NK8n25cdmWHsKCtF61, which is the output from hashing a metadata JSON, roughly something like:

{
  "name": "My Cool NFT",
  "description": "Description of the coolest NFT", 
  "media": "ipfs://QmWc6YHE815F8kExchG9kd2uSsv7ZF1iQNn23bt5iKC6K3"
}

NFT.js

// Global Token ID counter
Counter = 0

// Mapping from Token ID to user wallet address
Database = Map<int, address>{}

// Mapping from Token ID to its associated metadata
TokenMetadatas = Map<int, string>{}

// Mint/create a NFT and assign it to a new wallet address
function CreateToken (ownerAddress, metadata) {
  // Optional: restrictions such as who can mint, enforce limited edition or 1/1, etc
  if (Query.address != Artist) {
    throw "Only the Artist can create a new Token"
  }
  
  // Get a unique ID for the Token and increment global Counter
  id = Counter
  Counter += 1

  // Assign the unique Token ID to its new owner
  Database[id] = ownerAddress

  // Associate the token with data, eg: IPFS URI which describes media + info
  TokenMetadatas[id] = metadata
}

// Query the metadata (eg: IPFS URI) for the given Token ID
function TokenMetadata (id) {
  return TokenMetadatas[id]
}

// Query the wallet address that currently owns the specified Token ID
function OwnerOf (id) {
  return Database[id]
}

// Allow owner to transfer their token (NFT) from one wallet to another
function TransferToken (id, newOwnerAddress) {
  // Limit so that only the owner of that token can query this function
  if (Query.address != Database[id]) {
    throw "Only the current Token Owner can transfer their Token"
  }

  // Assign the Token ID to its new wallet address
  Database[id] = newOwnerAddress
}