ERC-721 Enumerable Burn Facet

ERC-721 token burning and enumeration tracking

Key Features

• Implements ERC-721 token burning.
• Integrates with diamond storage for enumeration tracking.
• Exposes burn function externally via the diamond proxy.
• Provides internal functions (getStorage, getERC721Storage) for accessing facet-specific and shared storage.

Overview

This facet implements ERC-721 token burning functionality within a Compose diamond. It exposes external functions for destroying tokens and integrates with diamond storage for enumeration tracking. Developers add this facet to manage token lifecycle and maintain correct token counts.

Storage

ERC721EnumerableStorage

Definition

struct ERC721EnumerableStorage {
  mapping(address owner => mapping(uint256 index => uint256 tokenId)) ownerTokens;
  mapping(uint256 tokenId => uint256 ownerTokensIndex) ownerTokensIndex;
  uint256[] allTokens;
  mapping(uint256 tokenId => uint256 allTokensIndex) allTokensIndex;
}

---

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.enumerable"))
ERC721_STORAGE_POSITION	bytes32	Diamond storage slot position for this module (Value: keccak256("erc721"))

Functions

burn

Burns (destroys) a token, removing it from enumeration tracking.

function burn(uint256 _tokenId) external;

Parameters:

Property	Type	Description
_tokenId	uint256	The ID of the token to burn.

---

exportSelectors

Exports the function selectors of the ERC721EnumerableBurnFacet This function is use as a selector discovery mechanism for diamonds

function exportSelectors() external pure returns (bytes memory);

Returns:

Property	Type	Description
-	bytes	selectors The exported function selectors of the ERC721EnumerableBurnFacet

Events

Signature:

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

Errors

Signature:

error ERC721NonexistentToken(uint256 _tokenId);

Signature:

error ERC721InsufficientApproval(address _operator, uint256 _tokenId);

Best Practices

Best Practice

• Ensure the ERC721EnumerableBurnFacet is properly registered with the diamond proxy.
• Initialize the diamond's storage for ERC-721 before adding this facet.
• Verify that the burn function's access control is configured appropriately for your diamond's security model.

Security Considerations

Security

The burn function is an external function and should have appropriate access controls implemented at the diamond level to prevent unauthorized token destruction. The function removes a token from enumeration tracking, which could affect other facets relying on token order or count. Errors ERC721NonexistentToken and ERC721InsufficientApproval are emitted if the token does not exist or if approval conditions are not met, respectively.

Was this helpful?

Last updated:March 13, 2026