Integration Guide

1. Deploy Your Own VRFConsumerV2 Contract

The deployment parameters can be obtained from our official website: 🔗 APRO VRF Portal

Supported Chains

JuChain

Steps to Deploy

• Deploy your own VRFConsumerV2 contract

First, copy the contract code as follows to your local machine File 1 of 4 : LinkTokenInterface.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

interface LinkTokenInterface {
  function allowance(address owner, address spender) external view returns (uint256 remaining);

  function approve(address spender, uint256 value) external returns (bool success);

  function balanceOf(address owner) external view returns (uint256 balance);

  function decimals() external view returns (uint8 decimalPlaces);

  function decreaseApproval(address spender, uint256 addedValue) external returns (bool success);

  function increaseApproval(address spender, uint256 subtractedValue) external;

  function name() external view returns (string memory tokenName);

  function symbol() external view returns (string memory tokenSymbol);

  function totalSupply() external view returns (uint256 totalTokensIssued);

  function transfer(address to, uint256 value) external returns (bool success);

  function transferAndCall(address to, uint256 value, bytes calldata data) external returns (bool success);

  function transferFrom(address from, address to, uint256 value) external returns (bool success);
}

File 2 of 4 : VRFCoordinatorV2Interface.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

interface VRFCoordinatorV2Interface {
  /**
   * @notice Get configuration relevant for making requests
   * @return minimumRequestConfirmations global min for request confirmations
   * @return maxGasLimit global max for request gas limit
   * @return s_provingKeyHashes list of registered key hashes
   */
  function getRequestConfig() external view returns (uint16, uint32, bytes32[] memory);

  /**
   * @notice Request a set of random words.
   * @param keyHash - Corresponds to a particular oracle job which uses
   * that key for generating the VRF proof. Different keyHash's have different gas price
   * ceilings, so you can select a specific one to bound your maximum per request cost.
   * @param subId  - The ID of the VRF subscription. Must be funded
   * with the minimum subscription balance required for the selected keyHash.
   * @param minimumRequestConfirmations - How many blocks you'd like the
   * oracle to wait before responding to the request. See SECURITY CONSIDERATIONS
   * for why you may want to request more. The acceptable range is
   * [minimumRequestBlockConfirmations, 200].
   * @param callbackGasLimit - How much gas you'd like to receive in your
   * fulfillRandomWords callback. Note that gasleft() inside fulfillRandomWords
   * may be slightly less than this amount because of gas used calling the function
   * (argument decoding etc.), so you may need to request slightly more than you expect
   * to have inside fulfillRandomWords. The acceptable range is
   * [0, maxGasLimit]
   * @param numWords - The number of uint256 random values you'd like to receive
   * in your fulfillRandomWords callback. Note these numbers are expanded in a
   * secure way by the VRFCoordinator from a single random value supplied by the oracle.
   * @return requestId - A unique identifier of the request. Can be used to match
   * a request to a response in fulfillRandomWords.
   */
  function requestRandomWords(
    bytes32 keyHash,
    uint64 subId,
    uint16 minimumRequestConfirmations,
    uint32 callbackGasLimit,
    uint32 numWords
  ) external returns (uint256 requestId);

  /**
   * @notice Create a VRF subscription.
   * @return subId - A unique subscription id.
   * @dev You can manage the consumer set dynamically with addConsumer/removeConsumer.
   * @dev Note to fund the subscription, use transferAndCall. For example
   * @dev  LINKTOKEN.transferAndCall(
   * @dev    address(COORDINATOR),
   * @dev    amount,
   * @dev    abi.encode(subId));
   */
  function createSubscription() external returns (uint64 subId);

  /**
   * @notice Get a VRF subscription.
   * @param subId - ID of the subscription
   * @return balance - LINK balance of the subscription in juels.
   * @return reqCount - number of requests for this subscription, determines fee tier.
   * @return owner - owner of the subscription.
   * @return consumers - list of consumer address which are able to use this subscription.
   */
  function getSubscription(
    uint64 subId
  ) external view returns (uint96 balance, uint64 reqCount, address owner, address[] memory consumers);

  /**
   * @notice Request subscription owner transfer.
   * @param subId - ID of the subscription
   * @param newOwner - proposed new owner of the subscription
   */
  function requestSubscriptionOwnerTransfer(uint64 subId, address newOwner) external;

  /**
   * @notice Request subscription owner transfer.
   * @param subId - ID of the subscription
   * @dev will revert if original owner of subId has
   * not requested that msg.sender become the new owner.
   */
  function acceptSubscriptionOwnerTransfer(uint64 subId) external;

  /**
   * @notice Add a consumer to a VRF subscription.
   * @param subId - ID of the subscription
   * @param consumer - New consumer which can use the subscription
   */
  function addConsumer(uint64 subId, address consumer) external;

  /**
   * @notice Remove a consumer from a VRF subscription.
   * @param subId - ID of the subscription
   * @param consumer - Consumer to remove from the subscription
   */
  function removeConsumer(uint64 subId, address consumer) external;

  /**
   * @notice Cancel a subscription
   * @param subId - ID of the subscription
   * @param to - Where to send the remaining LINK to
   */
  function cancelSubscription(uint64 subId, address to) external;

  /*
   * @notice Check to see if there exists a request commitment consumers
   * for all consumers and keyhashes for a given sub.
   * @param subId - ID of the subscription
   * @return true if there exists at least one unfulfilled request for the subscription, false
   * otherwise.
   */
  function pendingRequestExists(uint64 subId) external view returns (bool);
}

File 3 of 4 : VRFConsumerBaseV2.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;

/** ****************************************************************************
 * @notice Interface for contracts using VRF randomness
 * *****************************************************************************
 * @dev PURPOSE
 *
 * @dev Reggie the Random Oracle (not his real job) wants to provide randomness
 * @dev to Vera the verifier in such a way that Vera can be sure he's not
 * @dev making his output up to suit himself. Reggie provides Vera a public key
 * @dev to which he knows the secret key. Each time Vera provides a seed to
 * @dev Reggie, he gives back a value which is computed completely
 * @dev deterministically from the seed and the secret key.
 *
 * @dev Reggie provides a proof by which Vera can verify that the output was
 * @dev correctly computed once Reggie tells it to her, but without that proof,
 * @dev the output is indistinguishable to her from a uniform random sample
 * @dev from the output space.
 *
 * @dev The purpose of this contract is to make it easy for unrelated contracts
 * @dev to talk to Vera the verifier about the work Reggie is doing, to provide
 * @dev simple access to a verifiable source of randomness. It ensures 2 things:
 * @dev 1. The fulfillment came from the VRFCoordinator
 * @dev 2. The consumer contract implements fulfillRandomWords.
 * *****************************************************************************
 * @dev USAGE
 *
 * @dev Calling contracts must inherit from VRFConsumerBase, and can
 * @dev initialize VRFConsumerBase's attributes in their constructor as
 * @dev shown:
 *
 * @dev   contract VRFConsumer {
 * @dev     constructor(<other arguments>, address _vrfCoordinator, address _link)
 * @dev       VRFConsumerBase(_vrfCoordinator) public {
 * @dev         <initialization with other arguments goes here>
 * @dev       }
 * @dev   }
 *
 * @dev The oracle will have given you an ID for the VRF keypair they have
 * @dev committed to (let's call it keyHash). Create subscription, fund it
 * @dev and your consumer contract as a consumer of it (see VRFCoordinatorInterface
 * @dev subscription management functions).
 * @dev Call requestRandomWords(keyHash, subId, minimumRequestConfirmations,
 * @dev callbackGasLimit, numWords),
 * @dev see (VRFCoordinatorInterface for a description of the arguments).
 *
 * @dev Once the VRFCoordinator has received and validated the oracle's response
 * @dev to your request, it will call your contract's fulfillRandomWords method.
 *
 * @dev The randomness argument to fulfillRandomWords is a set of random words
 * @dev generated from your requestId and the blockHash of the request.
 *
 * @dev If your contract could have concurrent requests open, you can use the
 * @dev requestId returned from requestRandomWords to track which response is associated
 * @dev with which randomness request.
 * @dev See "SECURITY CONSIDERATIONS" for principles to keep in mind,
 * @dev if your contract could have multiple requests in flight simultaneously.
 *
 * @dev Colliding `requestId`s are cryptographically impossible as long as seeds
 * @dev differ.
 *
 * *****************************************************************************
 * @dev SECURITY CONSIDERATIONS
 *
 * @dev A method with the ability to call your fulfillRandomness method directly
 * @dev could spoof a VRF response with any random value, so it's critical that
 * @dev it cannot be directly called by anything other than this base contract
 * @dev (specifically, by the VRFConsumerBase.rawFulfillRandomness method).
 *
 * @dev For your users to trust that your contract's random behavior is free
 * @dev from malicious interference, it's best if you can write it so that all
 * @dev behaviors implied by a VRF response are executed *during* your
 * @dev fulfillRandomness method. If your contract must store the response (or
 * @dev anything derived from it) and use it later, you must ensure that any
 * @dev user-significant behavior which depends on that stored value cannot be
 * @dev manipulated by a subsequent VRF request.
 *
 * @dev Similarly, both miners and the VRF oracle itself have some influence
 * @dev over the order in which VRF responses appear on the blockchain, so if
 * @dev your contract could have multiple VRF requests in flight simultaneously,
 * @dev you must ensure that the order in which the VRF responses arrive cannot
 * @dev be used to manipulate your contract's user-significant behavior.
 *
 * @dev Since the block hash of the block which contains the requestRandomness
 * @dev call is mixed into the input to the VRF *last*, a sufficiently powerful
 * @dev miner could, in principle, fork the blockchain to evict the block
 * @dev containing the request, forcing the request to be included in a
 * @dev different block with a different hash, and therefore a different input
 * @dev to the VRF. However, such an attack would incur a substantial economic
 * @dev cost. This cost scales with the number of blocks the VRF oracle waits
 * @dev until it calls responds to a request. It is for this reason that
 * @dev that you can signal to an oracle you'd like them to wait longer before
 * @dev responding to the request (however this is not enforced in the contract
 * @dev and so remains effective only in the case of unmodified oracle software).
 */
abstract contract VRFConsumerBaseV2 {
  error OnlyCoordinatorCanFulfill(address have, address want);
  // solhint-disable-next-line chainlink-solidity/prefix-immutable-variables-with-i
  address private immutable vrfCoordinator;

  /**
   * @param _vrfCoordinator address of VRFCoordinator contract
   */
  constructor(address _vrfCoordinator) {
    vrfCoordinator = _vrfCoordinator;
  }

  /**
   * @notice fulfillRandomness handles the VRF response. Your contract must
   * @notice implement it. See "SECURITY CONSIDERATIONS" above for important
   * @notice principles to keep in mind when implementing your fulfillRandomness
   * @notice method.
   *
   * @dev VRFConsumerBaseV2 expects its subcontracts to have a method with this
   * @dev signature, and will call it once it has verified the proof
   * @dev associated with the randomness. (It is triggered via a call to
   * @dev rawFulfillRandomness, below.)
   *
   * @param requestId The Id initially returned by requestRandomness
   * @param randomWords the VRF output expanded to the requested number of words
   */
  // solhint-disable-next-line chainlink-solidity/prefix-internal-functions-with-underscore
  function fulfillRandomWords(uint256 requestId, uint256[] memory randomWords) internal virtual;

  // rawFulfillRandomness is called by VRFCoordinator when it receives a valid VRF
  // proof. rawFulfillRandomness then calls fulfillRandomness, after validating
  // the origin of the call
  function rawFulfillRandomWords(uint256 requestId, uint256[] memory randomWords) external {
    if (msg.sender != vrfCoordinator) {
      revert OnlyCoordinatorCanFulfill(msg.sender, vrfCoordinator);
    }
    fulfillRandomWords(requestId, randomWords);
  }
}

File 4 of 4 : VRFConsumerV2.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import {LinkTokenInterface} from "./interfaces/LinkTokenInterface.sol";
import {VRFCoordinatorV2Interface} from "./interfaces/VRFCoordinatorV2Interface.sol";
import {VRFConsumerBaseV2} from "./VRFConsumerBaseV2.sol";

contract VRFConsumerV2 is VRFConsumerBaseV2 {
  uint256[] public s_randomWords;
  uint256 public s_requestId;
  VRFCoordinatorV2Interface internal COORDINATOR;
  LinkTokenInterface internal LINKTOKEN;
  uint64 public s_subId;
  uint256 public s_gasAvailable;

  constructor(address vrfCoordinator, address link) VRFConsumerBaseV2(vrfCoordinator) {
    COORDINATOR = VRFCoordinatorV2Interface(vrfCoordinator);
    LINKTOKEN = LinkTokenInterface(link);
  }

  function fulfillRandomWords(uint256 requestId, uint256[] memory randomWords) internal override {
    require(requestId == s_requestId, "request ID is incorrect");

    s_gasAvailable = gasleft();
    s_randomWords = randomWords;
  }

  function createSubscriptionAndFund(uint96 amount) external {
    if (s_subId == 0) {
      s_subId = COORDINATOR.createSubscription();
      COORDINATOR.addConsumer(s_subId, address(this));
    }
    // Approve the link transfer.
    LINKTOKEN.transferAndCall(address(COORDINATOR), amount, abi.encode(s_subId));
  }

  function topUpSubscription(uint96 amount) external {
    require(s_subId != 0, "sub not set");
    // Approve the link transfer.
    LINKTOKEN.transferAndCall(address(COORDINATOR), amount, abi.encode(s_subId));
  }

  function updateSubscription(address[] memory consumers) external {
    require(s_subId != 0, "subID not set");
    for (uint256 i = 0; i < consumers.length; i++) {
      COORDINATOR.addConsumer(s_subId, consumers[i]);
    }
  }

  function requestRandomness(
    bytes32 keyHash,
    uint64 subId,
    uint16 minReqConfs,
    uint32 callbackGasLimit,
    uint32 numWords
  ) external returns (uint256) {
    s_requestId = COORDINATOR.requestRandomWords(keyHash, subId, minReqConfs, callbackGasLimit, numWords);
    return s_requestId;
  }
}

• Open the contract code using Remix, as shown below.

• Switch to the compilation tab, select the compilation version, and compile the contract code.

• Switch to the deployment tab, select the compilation version, and link your wallet address

• In step 7 shown in the image above, enter the VRF Coordinator V2 address and link(Valueless Token) address and then click "transact" Finally，as shown in the image, you can copy your VRFConsumerV2 contract address in step nine, which will be used later.

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2. Create a Subscription

1. Open the VRF Subscription Manager: 🔗 Subscription Manager

2. Connect your wallet (top-right corner) and click "Create Subscription".

3. The Admin Address field is auto-filled with your connected wallet address.

4. Once created, an alert will confirm the subscription, and you'll be redirected to the dashboard.

5. Locate your Subscription ID in the "My Subscriptions" list.

---

3. Add a Consumer

1. On the subscription details page, click "Add Consumer".

2. Enter the address of your consuming contract and confirm the addition.

3. Approve the transaction in MetaMask or your wallet extension.

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4. Fund Your Subscription

To fund your subscription, provide:

• Your wallet address

• Your Subscription ID

Then, contact us via: 📧 Email: [email protected] 💬 Telegram: Head of Business Development

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5. Request Randomness

Call the requestRandomness function in the VRFConsumerV2 contract

solidity function requestRandomness(
    bytes32 keyHash,
    uint64 subId,
    uint16 minReqConfs,
    uint32 callbackGasLimit,
    uint32 numWords
)

Example Input

solidity [
    0x138eb5545472d2c19c8b6fa582ce5e9b6fdc37296e9aa87e6daad34d3df1cf64,//KeyHash
    2,    // Subscription ID
    3,    // Minimum request confirmations
    100000,  // Callback gas limit
    1     // Number of random words
]

Retrieve Randomness

Call the s_randomWords function in the VRFConsumerV2 contract to get the random number.

• Enter the index (starting from 0, max = numWords - 1).

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6. VRF Information

6.1 JuChain Mainnet

Contracts

Contracts Description	Contract Address
Valueless Token	0x95999b404aA3963E950bFE22A68cB973fFCC32DE
BlockHashStore	0xC6D770E144812985fe617CdB17E255a55653Cd7e
VRF Coordinator V2	0xA97de6a5AbaA9C2fA63e2d2A044B649B004C0151

VRF KeyHash Info

VRF KeyHash Description	Contract Address
KeyHash 1 (Max Gas: 5 GWEI)	0x5aa3d37efe5614ab2d4e35edd79e215bac5b91698c78ce99da0f6419ba860998
KeyHash 2 (Max Gas: 10 GWEI)	0x19670c32fd942860259b58780c8855d24c7ea5d4b81dcc2433e0c54f9cc379fe
KeyHash 3 (Max Gas: 15 GWEI)	0xd8482d5aaa74155c245a2a2dde0f3c83d10797c742ccd025ae59034f5b6b0130

6.2 JuChain Testnet

Contracts

Contracts Description	Contract Address
Valueless Token	0x4fdBbd424DB2959327c7764305afC31E86b87B5D
BlockHashStore	0x396861A1a9190CA43E1046a31eff98CF8492a265
VRF Coordinator V2	0xDcc49bF6415bd1dD639a42E87ef737e8d9288d06

VRF KeyHash Info

Contracts Description	Contract Address
KeyHash 1 (Max Gas: 5 GWEI)	0x138eb5545472d2c19c8b6fa582ce5e9b6fdc37296e9aa87e6daad34d3df1cf64
KeyHash 2 (Max Gas: 10 GWEI)	0x742b53394213d3d8e598b0df333f5c20a5481829c5d5fbddd50a6694fa14042e