ERC-721 Mint Module

Mint ERC-721 tokens using diamond storage

Key Features

• Exposes internal mint function for facet integration.
• Utilizes diamond storage pattern (EIP-8042) for state management.
• Emits Transfer event upon successful minting.
• No external dependencies, ensuring minimal on-chain footprint.

Module Usage

This module provides internal functions for use in your custom facets. Import it to access shared logic and storage.

Overview

This module provides internal functions to mint new ERC-721 tokens. Facets can import this module to manage token creation, leveraging shared diamond storage for consistency. Changes made via this module are immediately visible to all facets sharing the same storage.

Storage

ERC721Storage

Definition

struct ERC721Storage {
  mapping(uint256 tokenId => address owner) ownerOf;
  mapping(address owner => uint256 balance) balanceOf;
  mapping(address owner => mapping(address operator => bool approved)) isApprovedForAll;
  mapping(uint256 tokenId => address approved) approved;
}

State Variables

Property	Type	Description
STORAGE_POSITION	bytes32	Diamond storage slot position for this module (Value: keccak256("erc721"))

Functions

getStorage

Returns the ERC-721 storage struct from its predefined slot. Uses inline assembly to access diamond storage location.

function getStorage() pure returns (ERC721Storage storage s);

Returns:

Property	Type	Description
s	ERC721Storage	The storage reference for ERC-721 state variables.

---

mint

Mints a new ERC-721 token to the specified address. Reverts if the receiver address is zero or if the token already exists.

function mint(address _to, uint256 _tokenId) ;

Parameters:

Property	Type	Description
_to	address	The address that will own the newly minted token.
_tokenId	uint256	The ID of the token to mint.

Events

Emitted when ownership of a token changes, including minting and burning.

Signature:

event Transfer(address indexed _from, address indexed _to, uint256 indexed _tokenId);

Parameters:

Property	Type	Description
_from	address	The address transferring the token, or zero for minting.
_to	address	The address receiving the token, or zero for burning.
_tokenId	uint256	The ID of the token being transferred.

Errors

Thrown when the receiver address is invalid (e.g., zero address).

Signature:

error ERC721InvalidReceiver(address _receiver);

Thrown when the sender address is invalid (e.g., zero address).

Signature:

error ERC721InvalidSender(address _sender);

Best Practices

Best Practice

• Ensure the calling facet enforces access control before invoking mint.
• Verify the to address is not the zero address and the tokenId does not already exist before calling mint.
• Handle ERC721InvalidReceiver and other potential errors gracefully.

Integration Notes

Shared Storage

This module accesses shared diamond storage at the position identified by keccak256(\"erc721\") to manage ERC-721 token state. The mint function reads and writes to this shared storage. Any facet that also accesses this storage slot will observe changes made by this module immediately. The ERC721Storage struct, though empty in this definition, reserves the storage slot for future ERC-721 specific state.

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Last updated:March 13, 2026