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chainlink VRF中文教程（含mock），解决error： Arithmetic Underflow in createSubscription

news 2025/7/19 15:20:07

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我使用的版本：chainlink-brownie-contracts version:1.3.0

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1. Import 相关包
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import {VRFConsumerBaseV2Plus} from "@chainlink/contracts/src/v0.8/vrf/dev/VRFConsumerBaseV2PLUS.sol";
import {VRFV2PlusClient} from "@chainlink/contracts/src/v0.8/vrf/dev/libraries/VRFV2PlusClient.sol";
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2. 要使用的VRF功能的 contract 继承 VRFConsumerBaseV2Plus
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contract EnterDungeon is VRFConsumerBaseV2Plus{}
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3. 在contract中声明下列VRF状态变量
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// Chainlink VRF Variables
uint256 private immutable i_subscriptionId;
bytes32 private immutable i_gasLane; // keyHash
uint32 private immutable i_callbackGasLimit;
uint16 private constant REQUEST_CONFIRMATIONS = 3;
uint32 private constant NUM_WORDS = 1;
bool private s_enableNativePayment; // true:ETH, false:LINK
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4. 重构你的 contract 的 constructor
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constructor(address _vrfCoordinator, uint256 _subscriptionId, bytes32 _gasLane, uint32 _callbackGasLimit) VRFConsumerBaseV2Plus(_vrfCoordinator) {
i_subscriptionId = _subscriptionId;
i_gasLane = _gasLane;
i_callbackGasLimit = _callbackGasLimit;
}
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5. 实现 requestRandomNumber()，用来封装随机数请求的逻辑
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/**
* @notice requestRandomNumber
* @dev 自己定义的一个函数，可以叫做任何名字，只是单独封装了VRF请求随机数的逻辑
* @return requestId
*/
function requestRandomNumber() public returns (uint256 requestId) {
requestId = s_vrfCoordinator.requestRandomWords(
VRFV2PlusClient.RandomWordsRequest({
keyHash: i_gasLane,
subId: i_subscriptionId,
requestConfirmations: REQUEST_CONFIRMATIONS,
callbackGasLimit: i_callbackGasLimit,
numWords: NUM_WORDS,
extraArgs: VRFV2PlusClient._argsToBytes(VRFV2PlusClient.ExtraArgsV1({nativePayment: s_enableNativePayment}))
})
);
}
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6. 重写 fulfillRandomWords() 里面写你具体的业务逻辑
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/**
* @notice fulfillRandomWords
* @dev 当VRF请求随机数成功后，会调用这个函数，里面是拿到随机数后的具体处理逻辑
* 调用者是 VRF Coordinator，要使用requestId映射playerAddress
* @param requestId 请求ID
* @param randomWords 随机数
*/
function fulfillRandomWords(uint256 requestId, uint256[] calldata randomWords) internal override {
// TODO:
}
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7. 本地 Mock 测试

7.1 导入 Mock 合约
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import {VRFCoordinatorV2_5Mock} from "@chainlink/contracts/src/v0.8/vrf/mocks/VRFCoordinatorV2_5Mock.sol";
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7.2 部署 Mock 合约
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// 1. deploy vrfCoordinatorV2_5Mock
vrfCoordinatorV2_5Mock = new VRFCoordinatorV2_5Mock(
MOCK_BASE_FEE,
MOCK_GAS_PRICE_LINK,
MOCK_WEI_PER_UINT_LINK
);

// 2. create subscription
uint256 subscriptionId = vrfCoordinatorV2_5Mock.createSubscription();

// 3. fund subscription
vrfCoordinatorV2_5Mock.fundSubscription(subscriptionId, FUND_LINK_AMOUNT);
// FUND_LINK_AMOUNT = 100000000000000000000 = 100 LINK

// 4. add consumer
vrfCoordinatorV2_5Mock.addConsumer(chainConfig.subscriptionId, address(consumer_addr));
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7.3 常见报错 & 解决

报错信息原因解决办法
Arithmetic underflow in createSubscription() mock 里用 blockhash(block.number - 1)，而本地链把前一区块 hash 置 0 把内部实现改成 blockhash(block.number)（已在下方补丁）

错误信息：

VRFCoordinatorV2_5Mock::createSubscription()
│ └─ ← [Revert] panic: arithmetic underflow or overflow (0x11)
└─ ← [Revert] panic: arithmetic underflow or overflow (0x11)

补丁示例：

// SubscriptionApi.sol 片段
subId = uint256(
keccak256(
abi.encodePacked(
msg.sender,
blockhash(block.number), // ← 修改
address(this),
s_currentSubNonce
)
)
);

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🔗 线上部署别忘记

在 [Chainlink-VRF-UI](https://vrf.chain.link/) 手动 Add Consumer，否则主网请求将被拒绝。

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