DailyProgress_0808 - Githubissues

ChainLink提供VRF服务的介绍

目前ChainLink VRF只在以太坊上有支持

V2协议规定了几个角色：

使用VRF服务的账户，一般是smart contract的地址
支付VRF服务费的账户，我们称之为Subscription account，对应于一个Subscription ID.
- 该账户数据中有地址列表，只有在列表中的地址(实际为smart contract)，subscription account才会为它买单
- Subscription ID，会在下面的contract中被使用，指示该contract产生的费用由Subscrition ID对应账户来支付
管理VRF订阅的账户，我们称之为Subscription Owner，只有它有权限，把新的smart contract地址加入到subscript account的账户列表中和从账户列表中删除smart contract地址

所以这样的模型，把支付者，使用者，管理者的角色分开了，能支持客户灵活的业务逻辑

Chainlink还有每次使用VRF的gas和费用的limit的更详细的规定，这里就不讲述了。

使用VRF也很简单，在以太坊上部署一个合约，可以参考ChainLink的demo, 我添加一些简单的描述:

// An example of a consumer contract that relies on a subscription for funding.
pragma solidity ^0.8.7;

import "@chainlink/contracts/src/v0.8/interfaces/VRFCoordinatorV2Interface.sol";
import "@chainlink/contracts/src/v0.8/VRFConsumerBaseV2.sol";

/**
 * 切勿在生产环境中使用.
 */

contract VRFv2Consumer is VRFConsumerBaseV2 {
  VRFCoordinatorV2Interface COORDINATOR;

  // Your subscription ID.
  uint64 s_subscriptionId;

  // Rinkeby coordinator.   跟我们contract使用VRF对接的ChainLink合约方(ChainLink管它叫coordinator)
  // see https://docs.chain.link/docs/vrf-contracts/#configurations
  address vrfCoordinator = 0x6168499c0cFfCaCD319c818142124B7A15E857ab;

  // gas费用和callback等费用的设置，这里就不写了
  bytes32 keyHash = 0xd89b2bf150e3b9e13446986e571fb9cab24b13cea0a43ea20a6049a85cc807cc;
  ..................
  uint32 callbackGasLimit = 100000;

  // The default is 3, but you can set this higher.
  uint16 requestConfirmations = 3;

  // For this example, retrieve 2 random values in one request.
  // Cannot exceed VRFCoordinatorV2.MAX_NUM_WORDS.
  uint32 numWords =  2;

  uint256[] public s_randomWords;
  uint256 public s_requestId;
  address s_owner;    //部署合约的账户，即为Subscription Owner，它也有权修改订阅服务列表

  constructor(uint64 subscriptionId) VRFConsumerBaseV2(vrfCoordinator) {
    COORDINATOR = VRFCoordinatorV2Interface(vrfCoordinator);
    s_owner = msg.sender;
    s_subscriptionId = subscriptionId;
  }

  // Assumes the subscription is funded sufficiently.
  // 调用获取VRF的入口函数
  function requestRandomWords() external onlyOwner {
    // Will revert if subscription is not set and funded.
    s_requestId = COORDINATOR.requestRandomWords(
      keyHash,
      s_subscriptionId,
      requestConfirmations,
      callbackGasLimit,
      numWords
    );
  }

  // 该函数是留给coordinator完成VRF后callback contract的接口
  function fulfillRandomWords(
    uint256, /* requestId */
    uint256[] memory randomWords
  ) internal override {
    s_randomWords = randomWords;
  }

  modifier onlyOwner() {
    require(msg.sender == s_owner);
    _;
  }
}

至于Subscription Owner的角色，基本操作就是创建Subscription account，为Subscription account充值，维护将要使用VRF smart contract的地址列表，我们可以从web页面（Subscription Manager page）上来做，也可以用合约代码来做

Change the list of approved subscription consumers with addConsumer(uint64 subId, address consumer) or removeConsumer(uint64 subId, address consumer).

Transfer the subscription ownership with requestSubscriptionOwnerTransfer(uint64 subId, address newOwner) and acceptSubscriptionOwnerTransfer(uint64 subId).

View the subscription with getSubscription(uint64 subId). Cancel the subscription with cancelSubscription(uint64 subId).

To send LINK to the subscription balance, use the LINK token interface with LINKTOKEN.transferAndCall(address(COORDINATOR), amount, abi.encode(subId));. Any wallet can fund a subscription.

总体来说，ChainLink的文档写的很棒

jackalchenxu / jackalchenxu

DailyProgress_0808 #22

ChainLink提供VRF服务的介绍