lesson-9 solidity error

[TimeKeyRoll]

Hi there! I can't compile since there is an error. anyone knows about this?

[TimeKeyRoll]

raffle.sol

//SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;
import "@chainlink/contracts/src/v0.8/VRFConsumerBaseV2.sol";

error Raffle__NotEnoughEth();

contract Raffle is VRFConsumerBaseV2 {
    /*State Variable*/
    uint256 private immutable i_entranceFee;
    address payable[] private s_players;
    /* events */
    //events name could be reversed name of the function
    event RaffleEnter(address indexed player);

    constructor(address vrfCoordinatorV2, uint256 entranceFee) VRFConsumerBaseV2(vrfCoordinatorV2) {
        i_entranceFee = entranceFee;
    }

    function enterRaffle() public payable {
        // > bigger
        // require(msg.value> i_entranceFee, "not enough funds")
        if (msg.value < i_entranceFee) {
            revert Raffle__NotEnoughEth();
        }
        s_players.push(payable(msg.sender));
        emit RaffleEnter(msg.sender);
    }

    // function requestRandomWinner() external {
    //     //get random number
    //     //do something with it
    //     //this is 2 transaction process so no one can manipulate
    // }

    // function fulfillRandomWords() internal override {}

    /* view and pure */

    function getEntranceFee() public view returns (uint256) {
        return i_entranceFee;
    }

    function getPlayers(uint256 index) public view returns (address) {
        return s_players[index];
    }
}

[TimeKeyRoll]

error

PS D:\hardhat-lottery-fcc> npx hardhat compile
TypeError: Contract "Raffle" should be marked as abstract.
 --> contracts/raffle.sol:7:1:
  |
7 | contract Raffle is VRFConsumerBaseV2 {
  | ^ (Relevant source part starts here and spans across multiple lines).
Note: Missing implementation: 
   --> @chainlink/contracts/src/v0.8/VRFConsumerBaseV2.sol:122:3:
    |
122 |   function fulfillRandomWords(uint256 requestId, uint256[] memory randomWords) internal virtual;
    |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


Error HH600: Compilation failed

[othaime-en]

Hey @MasterofBlockchain you mostly get this error if you are inheriting a contract and you haven't implemented some functions contained in the contract you are have inherited. For example, if your contract has inherited an interface that has a randomFunction() function declared, you need to make sure that your contract has the same function randomFunction() implemented somewhere within your code.
In this case, the contract VRFConsumerBaseV2 has a function fulfillRandomWords() that you haven't implemented in your Raffle contract.
A simple fix would be to uncomment the line // function fulfillRandomWords() internal override {}

[TimeKeyRoll]

after uncommenting it ..still i have an error

PS D:\hardhat-lottery-fcc> npx hardhat compile
TypeError: Function has override specified but does not override anything.
  --> contracts/raffle.sol:35:44:
   |
35 |     function fulfillRandomWords() internal override {}
   |                                            ^^^^^^^^


TypeError: Contract "Raffle" should be marked as abstract.
 --> contracts/raffle.sol:7:1:
  |
7 | contract Raffle is VRFConsumerBaseV2 {
  | ^ (Relevant source part starts here and spans across multiple lines).
Note: Missing implementation: 
   --> @chainlink/contracts/src/v0.8/VRFConsumerBaseV2.sol:122:3:
    |
122 |   function fulfillRandomWords(uint256 requestId, uint256[] memory randomWords) internal virtual;
    |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


Error HH600: Compilation failed

For more info go to https://hardhat.org/HH600 or run Hardhat with --show-stack-traces
PS D:\hardhat-lottery-fcc>

[othaime-en]

You are getting the error because you need to include some functionality inside your implementation of fulfillRandomWords() since the function has an override specifier. What do you want to use the VRFConsumerBaseV2 contract for? Are you trying to replicate the Raffle contract that we have on the course or are you creating your own different implementation?

[TimeKeyRoll]

I am following along with the course. Patrick did write this function like i have written and compiled it to show if its working fine. that's what im trying to do. :/

This is the scneehsot from patrick"s video.

[TimeKeyRoll]

if incase @othaime-en you would like to check repo - https://github.com/MasterofBlockchain/hardhat-lottery-fcc.git

[othaime-en]

Okay I'll check it. What is the timeline in the video?

[TimeKeyRoll]

14.14. 26 where he compiled.

[othaime-en]

Hey @MasterofBlockchain you failed to include the input parameters for the fulfillRandomWords() function. Add these as input parameters in that function uint256 requestId, uint256[] memory randomWords
The function should therefore be:

function fulfillRandomWords(uint256 requestId, uint256[] memory randomWords) internal override {}

Checkout 14.13.30 You missed it.

[TimeKeyRoll]

https://docs.chain.link/docs/vrf/v2/examples/get-a-random-number/

[othaime-en]

Oh. I understand your confusion now. What you see here is an example of how we can use VRFConsumerBaseV2. Don't you see that they are also importing the same contract (VRFConsumerBaseV2) in the imports section meaning that this is not the real contract, the real contract is at @chainlink/contracts/src/v0.8/VRFConsumerBaseV2.sol thats what you should be focusing on.
What you see here is a contract, like ours that is also trying to interact with the VRFConsumerBaseV2 and so its constructor ought to be different than ours because the contracts are also different. I hope you get it now.

[TimeKeyRoll]

lol i have marked as red but addresses are same man. what ya trying to say

[othaime-en]

By not the real contract I mean, the contract that you are seeing when you go to the link you have given me is not the real contract for VRFConsumerBaseV2 the real contract is at @chainlink/contracts/src/v0.8/VRFConsumerBaseV2.sol
You said that the constructor was different right? and you gave me the constructor below

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

Well, this constructor is not for our VRFConsumerBaseV2 contract it belongs to the contract in the link you have given me (the same example contract that I said is not the real VRFConsumerBaseV2 contract). Get it?

[TimeKeyRoll]

lol yes. thankyou very much.

[krakxn]

The error occurs when you inherit a contract (class) but do not use its functions (state).

Refer abstraction, an OOP concept.

[adityabhattad2021]

I feel you @MasterofBlockchain, but as we get deeper in this programming stuff technical answers are helpful too.

[TimeKeyRoll]

I understand we are into technical things and answer are gonna be technical but I prefer to have them in a easy way. They still would be technical but easy for others to grasp.So one can actual relate. But yes with time will learn things.

[krakxn]

It is actually very simple! You should refer to OOP core principles. The terms seem very daunting at first, but they indeed are very easy. Also, when you get into it you will realize how prevalent and vital they are.

Why? They are a fundamental concept in software engineering; you will notice it everywhere in some way. Solidity is inherently an OOP language too :)

[TimeKeyRoll]

So is this a feature of programming or is this itself a language!?
What resources are useful to look at!?
Do I have to study as core or study as to get basic idea!?

What would your opnion on that @krakxn

[krakxn]

It is a "concept" so fundamental to software engineering that it is involved in almost all the prominent programming languages.

In fact, you have already used all the OOP concepts to some extent throughout the course.

Honestly, a quick search on YT should yield satisfactory resources. FCC (or a video with a lot of views) should be enough.

[kihiuFrank]

@MasterofBlockchain @othaime-en
I'm also facing the same error despite having included the input parameters below as given in the answer.

uint256 requestId, uint256[] memory randomWords

I'm having 2 errors.
The first error is;
Function has override specified but does not override anything.

The second error is as below, but I think it has something to do with the first one.

Compilation Error;

TypeError: Function has override specified but does not override anything.
  --> contracts/Raffle.sol:54:91:
   |
54 |     function fulfillRandonWords(uint256 requestId, uint256[] memory randomWords) internal override {
   |                                                                                           ^^^^^^^^


TypeError: Contract "Raffle" should be marked as abstract.
  --> contracts/Raffle.sol:18:1:
   |
18 | contract Raffle is VRFConsumerBaseV2 {
   | ^ (Relevant source part starts here and spans across multiple lines).
Note: Missing implementation: 
   --> @chainlink/contracts/src/v0.8/VRFConsumerBaseV2.sol:122:3:
    |
122 |   function fulfillRandomWords(uint256 requestId, uint256[] memory randomWords) internal virtual;
    |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


Error HH600: Compilation failed

While researching, I have seen that this can be caused by functions you need to implement in your contract from an inherited contract, but they are undefined in your contract. You need to include them somewhere.

The only other function I see in the VRFConsumerBaseV2.sol is rawFulfillRandomWords() but in the tutorial, it wasn't included in the Raffle.sol

Tutorial timetamp; 14:12:47

See both contracts below if needed.

Raffle.sol

// Raffle tasks

// Enter the lottery (paying some amount)
// Pick a random winner (verifiably random)
// Winner to be selected every X minutes -> completely Automated

// Chainlink Oracle -> randomness, Automated Execution. And to trigger selectin a winner we will use; (Chainlink Keepers)

//------------------------------------------------------------------------------------------------------------------------------------------

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;

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

error Raffle__NotEnoughEthEntered();

contract Raffle is VRFConsumerBaseV2 {
    /* State Variables */
    uint256 private i_enteranceFee;
    address payable[] private s_prayers;

    /* Events */
    event RaffleEnter(address indexed player);

    constructor(address vrfCoordinatorV2, uint256 enteranceFee)
        VRFConsumerBaseV2(vrfCoordinatorV2)
    {
        i_enteranceFee = enteranceFee;
    }

    function enterRaffle() public payable {
        // you can do this,
        //require (msg.value > i_enteranceFee, "Not Enough ETH!")

        // but we will use error codes for gas efficiency since storing strings if supper expensive
        if (msg.value < i_enteranceFee) {
            revert Raffle__NotEnoughEthEntered();
        }
        s_prayers.push(payable(msg.sender));

        //Emit an event when we update a dynamic array or mapping
        //name events with fuction name reversed. in this case event RaffleEnter()
        emit RaffleEnter(msg.sender);
    }

    function requestRandomWinner() external {
        //Request random number
        // then do something with it
        // chainlink VRF is a 2 transaction process
    }

    function fulfillRandonWords(uint256 requestId, uint256[] memory randomWords)
        internal
        override
    {}

    /* view / pure functions */
    function getEnteranceFee() public view returns (uint256) {
        return i_enteranceFee;
    }

    function getPlayers(uint256 index) public view returns (address) {
        return s_prayers[index];
    }
}

VRFConsumerBaseV2.sol

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

/* REMOVED COMMENTS TO SHORTEN IT */

abstract contract VRFConsumerBaseV2 {
  error OnlyCoordinatorCanFulfill(address have, address want);
  address private immutable vrfCoordinator;

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

  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);
  }
}

[othaime-en]

Hey @kihiuFrank you've made a typo in your function declaration of fulfillRandomWords The function names need to be identical and I'm guessing that's where the error is coming from. Rename fulfillRandonWords as fulfillRandomWords (should be m not n).
Notify me if this fixes your issue.

[kihiuFrank]

@othaime-en Thanks so much. It's Fixed!
Still can't believe that's what made me stuck for so long. 😭

[othaime-en]

Glad I helped. All the best! :)