Lesson 9: Has anyone tried refactoring code to not emit RequestedRaffleWinner event?

[atenger]

In lesson 9, at around 15:47, Patrick explains we don't need this line of code in Raffle.sol:

emit RequestedRaffleWinner(requestId);

Because the VRFCoordinatorV2 function requestRandomWords emits a RandomWordsRequested event which includes requestId which we should be able to use.

emit RandomWordsRequested( _keyHash, requestId, preSeed, _subId, _minimumRequestConfirmations, _callbackGasLimit, _numWords, msg.sender );

In our Raffle.test.js code, we're testing to make sure we can get requestId from the logs after calling PerformUpkeep. Has anyone successfully refactored this?

I imagine the steps would be something along the lines of:

1. In Raffle.sol, delete the line emit RequestedRaffleWinner(requestId); from performUpkeep function
2. In Raffle.test.sol, change the test to get requestId from a different event

Anyone have any luck with this?

[othaime-en]

@PatrickAlphaC a little help here. :)

[atenger]

a little more detail...

Changes to raffle.sol:

Here's what performUpkeep looks like now.

I commented out emit RequestedRaffleWinner(requestId); in this function because the VRFCoordinatorV2Mock code for function requestRandomWords is emitting RandomWordsRequested event

    function performUpkeep(
        bytes calldata /*performData*/
    ) external override {
        //validate: Need to make sure this only gets called when checkup is true
        (bool upkeepNeeded, ) = checkUpkeep("");
        if (!upkeepNeeded) {
            revert Raffle__UpkeepNotNeeded(
                address(this).balance,
                s_players.length,
                uint256(s_raffleState)
            );
        }
        // Request a random number, and then once we get it, do something with it

        s_raffleState = RaffleState.CALCULATING;

        uint256 requestId = i_vrfCoordinater.requestRandomWords(
            i_gasLane, //gaslane
            i_subscriptionId,
            REQUEST_CONFIRMATIONS,
            i_callbackGasLimit,
            NUM_WORDS
        );

        // This is redundant, b/c the VRF Coordinator function request random words emits request iD
        //emit RequestedRaffleWinner(requestId);
    }

This is what I see in VRFCoordinatorMock2 - this is the event we need to access:

emit RandomWordsRequested(
      _keyHash,
      requestId,
      preSeed,
      _subId,
      _minimumRequestConfirmations,
      _callbackGasLimit,
      _numWords,
      msg.sender
    );

Changes to Raffle.test.sol:

This is the original PerformUpkeep test in Raffle.test.sol:

              it("updates the raffle state", async () => {
                  await raffle.enterRaffle({ value: raffleEntranceFee })
                  await network.provider.send("evm_increaseTime", [interval.toNumber() + 1])
                  await network.provider.request({ method: "evm_mine", params: [] })
                  const txResponse = await raffle.performUpkeep("0x") // emits requestId
                  const txReceipt = await txResponse.wait(1) // waits 1 block
                  const raffleState = await raffle.getRaffleState() // updates state
                  const requestId = txReceipt.events[1].args.requestId
                  assert(raffleState == 1) // 0 = open, 1 = calculating
              })

I figure I need to change this line:

const requestId = txReceipt.events[1].args.requestId

Instead of going to the events index at 1, I think I need to go to the events index at 0. But when I tried that I was getting an empty object and after playing around printing to console I got stuck and gave up.

[PatrickAlphaC]

You're so close! Have you tried the javascript debug in VSCode? You could see what your txReceipt object looks like and find the event number in there :)

[atenger]

Thanks for the encouragement & advice!! Being a newbie, I totally forgot about using the debugger (was using console.log statements). I've now added breakpoints so I can query the txReceipt object from the javascript debug console, but I'm still not able to find any other requestId except the one we emit.

I looked at both the txReceipt.events and txReceipt.logs and clearly see there is an event at index 0, which must be the one the VRFCoordinator is emitting, but when I play around with the object, I don't see anyway to find the requestId.

Any more advice @PatrickAlphaC ?

[othaime-en]

Hey @atenger and @PatrickAlphaC I think I cracked it. Okay so we know i_vrfCoordinater.requestRandomWords() method emits an event called RandomWordsRequested It is emitted in our Raffle contract but our contract doesn't have an event declaration for this said event. So i figured, what if I initialized/declared this RandomWordsRequested event in my raffle contract similar to the one in the VRFCoordinatorV2Mock. I mean we already know it is emitted (the first event at index 0), we just need to sort of catch it right? So I added this code in my raffle contract event sections

  event RandomWordsRequested(
    bytes32 indexed keyHash,
    uint256 requestId,
    uint256 preSeed,
    uint64 indexed subId,
    uint16 minimumRequestConfirmations,
    uint32 callbackGasLimit,
    uint32 numWords,
    address indexed sender
  );

So now, we can even request the arguments same as we did with the second event at index 1.
To test my theory, I did some console logging.

const requestId = txReceipt.events[0]   //notice I removed .args.requestId just to be sure first there was an event at index 0
console.log(requestId) 

And...whadyya know... there it was, the entire event and some other args. (Of course the test failed, but I just wanted to see if it worked)

Local network detected!!! Deploying Mock Contract...
{
  transactionIndex: 0,
  blockNumber: 8,
  transactionHash: '0xfd2266f578305aa69d54e350cc9459218282aa627ccd1b5bf58119a512d4d24b',
  address: '0x5FbDB2315678afecb367f032d93F642f64180aa3',
  topics: [
    '0x63373d1c4696214b898952999c9aaec57dac1ee2723cec59bea6888f489a9772',
    '0xd89b2bf150e3b9e13446986e571fb9cab24b13cea0a43ea20a6049a85cc807cc',
    '0x0000000000000000000000000000000000000000000000000000000000000001',
    '0x000000000000000000000000cf7ed3acca5a467e9e704c703e8d87f634fb0fc9'
  ],
  data: '0x000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000640000000000000000000000000000000000000000000000000000000000000003000000000000000000000000000000000000000000000000000000000007a1200000000000000000000000000000000000000000000000000000000000000001',
  logIndex: 0,
  blockHash: '0x760d9c782c2b474c81117d2f40f18b1afc0eaa8e21be184b1bb1a451926b7c1f',
// HERE ARE THE ARGS
  args: [
    '0xd89b2bf150e3b9e13446986e571fb9cab24b13cea0a43ea20a6049a85cc807cc',
    BigNumber { _hex: '0x01', _isBigNumber: true },
    BigNumber { _hex: '0x64', _isBigNumber: true },
    BigNumber { _hex: '0x01', _isBigNumber: true },
    3,
    500000,
    1,
    '0xCf7Ed3AccA5a467e9e704C703E8D87F634fB0Fc9',
    keyHash: '0xd89b2bf150e3b9e13446986e571fb9cab24b13cea0a43ea20a6049a85cc807cc',
    requestId: BigNumber { _hex: '0x01', _isBigNumber: true },    // HERE IS THE requestId
    preSeed: BigNumber { _hex: '0x64', _isBigNumber: true },
    subId: BigNumber { _hex: '0x01', _isBigNumber: true },
    minimumRequestConfirmations: 3,
    callbackGasLimit: 500000,
    numWords: 1,
    sender: '0xCf7Ed3AccA5a467e9e704C703E8D87F634fB0Fc9'
  ],
  decode: [Function (anonymous)],
  event: 'RandomWordsRequested',
  eventSignature: 'RandomWordsRequested(bytes32,uint256,uint256,uint64,uint16,uint32,uint32,address)',
  removeListener: [Function (anonymous)],
  getBlock: [Function (anonymous)],
  getTransaction: [Function (anonymous)],
  getTransactionReceipt: [Function (anonymous)]
}

So with this, I just replaced 1 with 0 in my initial code and I was good to go.
I had the option of commenting out the RequestedRAffleWinner event but I just left it there for versatility if I chose to use the second event instead.

Long story short, add this event declaration code in your raffle contract and replace events[1].args.requestId with events[0].args.requestId in your raffle.test.js

  event RandomWordsRequested(
    bytes32 indexed keyHash,
    uint256 requestId,
    uint256 preSeed,
    uint64 indexed subId,
    uint16 minimumRequestConfirmations,
    uint32 callbackGasLimit,
    uint32 numWords,
    address indexed sender
  );

[adityabhattad2021]

Hey @othaime-en you did an awesome job! but I just had some doubts as in here

event RandomWordsRequested(
    bytes32 indexed keyHash,
    uint256 requestId,
    uint256 preSeed,
    uint64 indexed subId,
    uint16 minimumRequestConfirmations,
    uint32 callbackGasLimit,
    uint32 numWords,
    address indexed sender
  );

requestId is not indexed so how are we still able to access it?
and how does adding this RandomWordsRequested event in our raffle.sol changes any thing as requestId is still not indexed here?

[othaime-en]

To make things clear, you do not need to mark a parameter indexed to retrieve it. Okay yes, marking a parameter indexed helps make it searchable in the topics section of your transaction receipt but you can still retrieve a variable even if it is not marked indexed. For instance, in the log I've shared above, you can find all the indexed variables in the topics section.

topics: [
    '0x63373d1c4696214b898952999c9aaec57dac1ee2723cec59bea6888f489a9772', // Disregard this. This is just the signature of the events
    '0xd89b2bf150e3b9e13446986e571fb9cab24b13cea0a43ea20a6049a85cc807cc',  // This was our first indexed parameter keyHash/gasLane
    '0x0000000000000000000000000000000000000000000000000000000000000001', // The subId
    '0x000000000000000000000000cf7ed3acca5a467e9e704c703e8d87f634fb0fc9'  // The sender
  ]

Non-indexed parameters can still be retrieved although they are mashed and ABI-encoded into the data part or our logs. Meaning that we need to have the abi to easily decode them. If you don't have the abi it becomes difficult to decode them.
Now in our case, (since we have the abi) we can find all the other parameters (including the indexed parameters) in the args section of our logs.

To read more about events and logs checkout this article by chainlink. It has a very useful video by @PatrickAlphaC about events. I highly recommend you check it out to understand more about events.

[adityabhattad2021]

Thanks!

[atenger]

@othaime-en BRILLIANT!! Bravo!!

Based on your findings, I also added the event declaration in my Raffle.sol to catch or capture the event emitted. And then I also went ahead and removed our own custom event and refactored my tests to pull from Event at index 0. I pushed my code to https://github.com/atenger/hardhat-smartcontract-lottery

woo-hoo! thanks again!

[othaime-en]

Good job!!! Really glad I helped you out. Thanks for giving me this challenge, wouldn't have figured this out if you didn't ask. I'll be sure to check out your repo.