Chainlink VRF v2.5 Implementation Guide

Overview

A step-by-step guide to implement Chainlink's Verifiable Random Function (VRF) v2.5 in your smart contracts.

Key Components

1. Consumer Contract: Handles random number requests and fulfillment
2. Subscription Management: Prepaid account for VRF usage
3. VRF Coordinator: Chainlink's verification and callback system

Workflow Summary

1. Consumer Contract Setup

• Create a consumer contract that inherits from VRFConsumerBaseV2Plus
• Initialize with your chain's VRF Coordinator address
• Store subscription ID and other configuration parameters

2. Subscription Management

1. Create a subscription through Chainlink VRF Dashboard
2. Fund subscription with either:
   • Native blockchain currency (ETH, MATIC, etc.)
   • LINK tokens
3. Add consumer contract address to authorized consumers

3. Request Configuration

When calling requestRandomWords from the VRF Coordinator, provide:

struct RandomWordsRequest {
  bytes32 keyHash;           // Gas lane identifier
  uint256 subId;             // Subscription ID
  uint16 requestConfirmations; // Block confirmations (typically 3)
  uint32 callbackGasLimit;   // Gas for fulfillment function
  uint32 numWords;           // Number of random values needed
  bytes extraArgs;           // Additional parameters (optional)
}

4. callback fulfullRandomWords by the coordinator

after requesting the number the coordinator will automatically callback fulfillRandomWords function upon completion the result can be logged in this function