# ERC4907A

[`erc721a/contracts/extensions/ERC4907A.sol`](https://github.com/chiru-labs/ERC721A/blob/main/contracts/extensions/ERC4907A.sol)

[ERC4907](https://eips.ethereum.org/EIPS/eip-4907) compliant extension of ERC721A, which allows owners and authorized addresses to add a time-limited role with restricted permissions to ERC721 tokens.

This implementation does **not** reset the user information upon token transfer. 
The new owner must call [`setUser`](#setUser) to change or reset the user.

To reset or alter the user information after each transfer, you will need to override either 
[`_beforeTokenTransfers`](erc721a.md#_beforeTokenTransfers) or 
[`_afterTokenTransfers`](erc721a.md#_afterTokenTransfers) in ERC721A.

Inherits:

- [ERC721A](erc721a.md)
- [IERC4907A](interfaces.md#ierc4907a) 


## Functions

### setUser

```solidity
function setUser(uint256 tokenId, address user, uint64 expires) public virtual
```

Sets the `user` and `expires` for `tokenId`.

The zero address indicates there is no user.

Requirements:

- The caller must own `tokenId` or be an approved operator.


### userOf 

```solidity
function userOf(uint256 tokenId) public view virtual returns (address)
```

Returns the user address for `tokenId`.

The zero address indicates that there is no user or if the user is expired.

### userExpires

```solidity
function userExpires(uint256 tokenId) public view virtual returns (uint256)
```

Returns the user's expires of `tokenId`.

### \_explicitUserOf

```solidity
function _explicitUserOf(uint256 tokenId) internal view virtual returns (address)
```

Returns the user address for `tokenId`, ignoring the expiry status.


## Events

### UpdateUser

`IERC4907-UpdateUser`

```solidity
event UpdateUser(uint256 indexed tokenId, address indexed user, uint64 expires)
```

Emitted when the `user` of an NFT or the `expires` of the `user` is changed.

The zero address for user indicates that there is no user address.