Follow Module Interface

This is the interface all Lens Protocol Compatible Follow modules must implement.

initializeFollowModule()

function initializeFollowModule(uint256 profileId, bytes calldata data) external;

This function initializes the follow module for a given Lens profile. The hub contract can only call this.

processFollow()

function processFollow(address follower, uint256 profileId, bytes calldata data) external;

This function processes a given follow; this can only be called from the LensHub contract.

followModuleTransferHook()

followModuleTransferHook(uint256 profileId, address from, address to, uint256 followNFTTokenId) external;

This is a transfer hook that is called upon follow NFT transfer in beforeTokenTransfer. This can only be called from the LensHub contract.

NOTE: Special care needs to be taken here: It is possible that follow NFTs were issued before this module was initialized if the profile's follow module was previously different. This transfer hook should consider this, especially when the module holds state associated with individual follow NFTs.

function validateFollow()

function validateFollow(uint256 profileId, address follower, uint256 followNFTTokenId) external view;

This is a helper function that could be used in conjunction with specific collect modules.

NOTE: This function IS meant to replace a check on follower NFT ownership.

NOTE: It is assumed that not all collect modules are aware of the token ID to pass. In these cases, this should receive a followNFTTokenId of 0, which is impossible regardless.

One example of a use case for this would be a subscription-based following system:
1. The collect module:
- Decodes a follower NFT token ID from user-passed data.
- Fetches the follow module from the hub.
- Calls validateFollow passing the profile ID, follower & follower token ID.
2. The follow module:
- Validates the subscription status for that given NFT, reverting on an invalid subscription.

Whitelisted Follow Modules

Approval Follow Module

The Approval Follow Module only allows addresses that are approved for a profile by the profile owner to follow. Users can use the approve() function to add/remove addresses from the Approved Array. the isApproved() or isApprovedArray() functions allow applications to check which address(es) are approved by a given user.

Fee Follow Module

The Fee Follow Module only allows addresses to follow a given profile, so long as they pay a fee specified by the profile owner. Users can set the currency and amount required to be paid so long as the currency has been whitelisted by governance. Additionally, governance can adjust the treasuryFee variable to direct some of the follow fees to a specified treasury address.