ERC-1155 Data Facet

View balances and approvals for ERC-1155 tokens

Key Features

• Exposes external view functions for ERC-1155 data retrieval.
• Reads from shared diamond storage for token balances and approvals.
• Supports batched queries for efficiency.
• Includes exportSelectors for diamond discovery.

Overview

This facet provides external read-only functions for ERC-1155 token balances and operator approvals within a diamond. It accesses shared diamond storage to retrieve this information, enabling consistent data retrieval across different facets. Developers integrate this facet to expose ERC-1155 data querying capabilities through the diamond proxy.

Storage

ERC1155Storage

Definition

struct ERC1155Storage {
  mapping(uint256 id => mapping(address account => uint256 balance)) balanceOf;
  mapping(address account => mapping(address operator => bool)) isApprovedForAll;
}

State Variables

Property	Type	Description
STORAGE_POSITION	bytes32	Diamond storage slot position for this module (Value: keccak256("erc1155"))

Functions

balanceOf

Returns the amount of tokens of token type id owned by account.

function balanceOf(address _account, uint256 _id) external view returns (uint256);

Parameters:

Property	Type	Description
_account	address	The address to query the balance of.
_id	uint256	The token type to query.

Returns:

Property	Type	Description
-	uint256	The balance of the token type.

---

balanceOfBatch

Batched version of balanceOf.

function balanceOfBatch(address[] calldata _accounts, uint256[] calldata _ids)
  external
  view
  returns (uint256[] memory balances);

Parameters:

Property	Type	Description
_accounts	address[]	The addresses to query the balances of.
_ids	uint256[]	The token types to query.

Returns:

Property	Type	Description
balances	uint256[]	The balances of the token types.

---

isApprovedForAll

Returns true if operator is approved to transfer account's tokens.

function isApprovedForAll(address _account, address _operator) external view returns (bool);

Parameters:

Property	Type	Description
_account	address	The token owner.
_operator	address	The operator to query.

Returns:

Property	Type	Description
-	bool	True if the operator is approved, false otherwise.

---

exportSelectors

Exports the function selectors of the ERC1155DataFacet 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 ERC1155DataFacet

Errors

Error indicating array length mismatch in batch operations.

Signature:

error ERC1155InvalidArrayLength(uint256 _idsLength, uint256 _valuesLength);

Best Practices

Best Practice

• Ensure the ERC1155DataFacet is added to the diamond with the correct selectors.
• Use balanceOfBatch for efficient retrieval of multiple balances to minimize gas costs.
• Verify that the ERC1155ApproveFacet or equivalent is also deployed to manage approvals.

Security Considerations

Security

This facet only exposes read-only functions. Input validation for array lengths is handled by the ERC1155InvalidArrayLength error in balanceOfBatch. Follow standard Solidity security practices for all interactions with the diamond.

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Last updated:March 13, 2026