> For the complete documentation index, see [llms.txt](https://docs.aera.finance/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.aera.finance/the-protocol/core/ibeforetransferhook.md).

# IBeforeTransferHook

Interface for token transfer hooks used for vault units in multi-depositor vaults

## Functions

### setIsVaultUnitsTransferable

Set whether vault units should be transferable

```solidity
function setIsVaultUnitsTransferable(address vault, bool isTransferable) external;
```

**Parameters**

| Name             | Type      | Description                              |
| ---------------- | --------- | ---------------------------------------- |
| `vault`          | `address` | The vault to update status for           |
| `isTransferable` | `bool`    | Whether the vault units are transferable |

### beforeTransfer

Perform before transfer checks

```solidity
function beforeTransfer(address from, address to, address transferAgent) external view;
```

**Parameters**

| Name            | Type      | Description                                          |
| --------------- | --------- | ---------------------------------------------------- |
| `from`          | `address` | Address that is sending the units                    |
| `to`            | `address` | Address that is receiving the units                  |
| `transferAgent` | `address` | Address that is always allowed to transfer the units |

## Events

### VaultUnitTransferableSet

Emitted when vault unit transferability is updated

```solidity
event VaultUnitTransferableSet(address indexed vault, bool isTransferable);
```

**Parameters**

| Name             | Type      | Description                              |
| ---------------- | --------- | ---------------------------------------- |
| `vault`          | `address` | The vault address                        |
| `isTransferable` | `bool`    | Whether the vault units are transferable |

## Errors

### Aera\_\_NotVaultOwner

```solidity
error Aera__NotVaultOwner();
```

### Aera\_\_VaultUnitsNotTransferable

```solidity
error Aera__VaultUnitsNotTransferable(address vault);
```


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