Hook

Hooks are functions that can be added to the Loyalty Point contract to extend its functionality. They are executed during token transfers and can be used to implement custom logic, such as access control, rewards distribution, or external event triggers.

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Creating a Hook

To create a hook, you need to implement the ILoyaltyPointHook interface:

interface ILoyaltyPointHook {
  function onUpdate(address from, address to, uint256 value) external returns (bool);
}

Now let’s see how to create a hook and add it to your Loyalty Point contract. For this example, we’ll create a hook that will trigger an event when user points are updated.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;

import "../interface/ILoyaltyPointHook.sol"; // Adjust the path as necessary

contract ExampleLoyaltyPointHook is ILoyaltyPointHook {
    // Event emitted when points are updated
    event PointsUpdated(
        address indexed from,
        address indexed to,
        uint256 value
    );

    // Implementing the onUpdate function
    function onUpdate(
        address from,
        address to,
        uint256 value
    ) external override returns (bool) {
        // Emit the PointsUpdated event
        emit PointsUpdated(from, to, value);
        return true; // Indicate success
    }
}

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Deploying the Hook

Set up the environment variables:

PRIVATE_KEY=<private-key>

Deploy the hook:

forge script script/DeployExampleLoyaltyPointHook.s.sol:DeployExampleLoyaltyPointHook --rpc-url <rpc-url> --broadcast

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Setup hook on Loyalty Point contract

Set up necessary environment variables:

PRIVATE_KEY=<private-key>
LOYALTY_POINT_ADDRESS=<loyalty-point-address>
HOOK_ADDRESS=<hook-address>

• PRIVATE_KEY: The private key of the admin account of the Loyalty Point contract.
• LOYALTY_POINT_ADDRESS: The address of the Loyalty Point contract.
• HOOK_ADDRESS: The address of the hook contract.

Add the hook to the Loyalty Point contract:

forge script script/AddHook.s.sol:AddHook --rpc-url <rpc-url> --broadcast

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Testing the Hook

You can test the hook by minting or burning points to a user. The hook should be triggered and the event should be emitted.

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Example

An example of a hook that distributes rewards to a user has been deployed here.

And here is a transaction that triggers the hook: 0xa4d01f742a1f532cecdb3b0c0a1a3b0922603cec4cf0edf46bd00c549ad03b75.

In the transaction logs, you can see that the hook is called and the PointsUpdated event is emitted.