# Follow
"Follow" is a term used on social media platforms to describe the act that a user follows another to monitor the latter's new posts. This increases interaction between users.
The "Follow" contract we provide is used to describe a one-way action of following.
## Schema
### FollowRegister
The [schema](https://arweave.net/auPfoCDBtJ3RJ_WyUqV9O7GAARDzkUT4TSuj9uuax-0) corresponding to the FollowRegister contract is saved to Arweave in the form of a ttl file, with the transaction hash as the schemaURI to be passed to the contract during its initialization stage. For example:
```
ar://auPfoCDBtJ3RJ_WyUqV9O7GAARDzkUT4TSuj9uuax-0
```
To describe the Follow contract address of a certain address, we can use the following rdf as an example:
```
:Soul_0x0000000000000000000000000000000000000011 p:connectionContract :Activity_0x12345678901111111000000000
```
* The list of prefixes.
```
PREFIX :
PREFIX p:
PREFIX rdf:
PREFIX xsd:
PREFIX rdfs:
```
* Class
":Soul" means the address for accepting and bounding a name. ":Contract" means the address of the "Follow" contract.
```
:Soul a rdfs:Class ;
rdfs:label "Soul" ;
rdfs:comment "A soul." .
:Contract a rdfs:Class ;
rdfs:label "Contract" ;
rdfs:comment "A contract." .
```
* Predicate
"p:followContract" is used to describe the addresses of the "follow" contracts owned by a particular address.
```
p:followContract a rdf:Property ;
rdfs:label "followContract" ;
rdfs:comment "The soul's follow contract." ;
rdfs:domain :Soul ;
rdfs:range :Contract .
```
### Follow
The [schema](https://arweave.net/-2hCuTMqo1fz2iyzf7dbEbzoyceod5KFOyGGqNiEQWY) corresponding to the Follow contract is saved to Arweave in the form of a ttl file, with the transaction hash as the schemaURI to be passed to the contract during its initialization stage. For example:
```
ar://-2hCuTMqo1fz2iyzf7dbEbzoyceod5KFOyGGqNiEQWY
```
To describe that certain address is following the owner of the current contract, we can use the following rdf as an example:
```
:Soul_0x0000000000000000000000000000000000000022 p:following :Soul_0x0000000000000000000000000000000000000011
```
* Prefix of a namespace.
```
PREFIX :
PREFIX p:
PREFIX rdf:
PREFIX xsd:
PREFIX rdfs:
```
* Class
":Soul" means the address for accepting and bounding a name. ":Contract" means the address of the "Follow" contract.
```
:Soul a rdfs:Class ;
rdfs:label "Soul" ;
rdfs:comment "A soul." .
```
* Predicate
"p:following" is used to describe the "follow" relationship between addresses.
```
p:following a rdf:Property ;
rdfs:label "following" ;
rdfs:comment "Following a soul." ;
rdfs:domain :Soul ;
rdfs:range :Soul .
```
## Contract
The contract template for the Follow contract. We use FollowRegister as the factory pattern and registration center to deploy and record a user's Follow contract.
### FollowRegister
```solidity
interface IFollowRegister is ISemanticSBT {
/**
* Deploy a follow contract.
* @param addr : The address to accept a Follow contract.
* @return tokenId
*/
function deployFollowContract(address addr) external returns (uint256);
/**
* Query the Follow contract address of a certain address.
* @param owner : The owner of the address of the Follow contract.
* @return contractAddress : The Follow contract address.
*/
function ownedFollowContract(address owner) external view returns (address);
}
```
### Follow
```solidity
interface IFollow is ISemanticSBT {
/**
* Initialize the contract
*/
function initialize(
address owner,
address minter,
string memory name_,
string memory symbol_,
string memory baseURI_,
string memory schemaURI_,
string[] memory classes_,
Predicate[] memory predicates_
) external;
/**
* Follow the owner of the current contract.
* @return tokenId
*/
function follow() external returns (uint256);
/**
* Unfollow
* @return tokenId
*/
function unfollow() external returns (uint256);
/**
* Returns whether the `addr` is following the owner of the current contract
* @return isFollowing
*/
function isFollowing(address addr) external view returns (bool);
}
```
### Contract implementation note
As a factory pattern, registration center and router contract, the "FollowRegister" has the following business logic:
* deployFollowContract: To deploy the "Follow" contract.
* ownedFollowContract: To query the "Follow" contract owned by an address.
As the contract actually records a user's "follow" relationships, "Follow" can be owned by each user. When a new fan follows a user, a token will be minted by the user's "Follow" contract and distributed to the fan.
* follow: A fan will mint a token via the "Follow" contract of the person he/she follows.
* unfollow: When a fan cancels the "follow" relationship and burns the token generated by that particular relationship.
Full source code:
* [FollowRegister](https://github.com/relationlabs/semanticSBT/blob/main/contracts/template/FollowRegister.sol)
* [Follow](https://github.com/relationlabs/semanticSBT/blob/main/contracts/template/Follow.sol)
---
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