Lesson 9 - ethers.getContract vs deployments.get in Raffle deployment script

[levblanc]

Hi,

I found we are getting the mock's address in a different way than previous lesson:

// Previous lesson
const ethUsdAggregator = await deployments.get('MockV3Aggregator');

// Lesson 9
const vrfCoordinatorV2Mock = await ethers.getContract(
      'VRFCoordinatorV2Mock'
);

and when I try to get VRFCoordinatorV2Mock address by using deployments.get, it will return error. Why?

In both lessons, we deployed MockV3Aggregator & VRFCoordinatorV2Mock in the 00-deploy-mocks.js script the same way.

Why is deployments.get not working for VRFCoordinatorV2Mock?

Thanks in advance.

[othaime-en]

@levblanc can you please share your lesson 9 code where you are trying get VRFCoordinatorV2Mock I need context

[levblanc]

Hi @othaime-en ,

My code is here:
https://github.com/levblanc/web3-lottery-hardhat/blob/master/deploy/01-deploy-raffle.js#L17

You could try Patrick's code as well, see links below.
Before I met this query, I was using deployments.get as in previous lesson and it returns error.
I referred to Patrick's code and found the difference. Just wondering why.

For VRFCoordinatorV2Mock:
https://github.com/PatrickAlphaC/hardhat-smartcontract-lottery-fcc/blob/main/deploy/01-deploy-raffle.js#L19

For MockV3Aggregator :
https://github.com/PatrickAlphaC/hardhat-fund-me-fcc/blob/main/deploy/01-deploy-fund-me.js#L12

[othaime-en]

Hi @levblanc I get the error you are talking about. I actually ran into it myself. deployments.get() and ethers.getContract have somewhat of a similar functionality, getting the latest deployed instance of whatever contract we specify. However, I noticed that they return very different object/instances hence the disparity in that raises this error. The nature of deployments.get() makes it hard to work with contracts in cases where we call the functions from the contract within our deploy scripts as evidenced by the lesson 9 error. ethers.getContract on the other hand is very reliable and versatile in both instances even when we have to call functions especially when deploying. So in short, my discovery was that in lesson 7 it was easy to use deployments.get() because we weren't calling any functions from the aggregator at that time so it worked just fine. However when it came to lesson 9 where we had to get the deployment and then create a subscription by calling a function from that instance we got back, we encountered an error. Hence we had to use ethers.getContract because it is versatile and is best when we have to call functions from the contract.
If you want to experiment, try and change the line fundMe = await ethers.getContract("FundMe", deployer) to fundMe = await deployments.get("FundMe", deployer) in your fundme.test.js or any other script where you call functions from a contract and see if it works. Hint: It most likely wont.

[levblanc]

Thanks for your reply.

You are right, deployments.get and ethers.getContract returns different info in an object.

deployments.get returns info for the deployment, not the contract:
https://github.com/wighawag/hardhat-deploy/blob/02416ec1fc18e6dd3e786e9d27a1576255059567/types.ts#L358

ethers.getContract returns info for the contract itself, including interact-able functions:
https://github.com/ethers-io/ethers.js/blob/ec1b9583039a14a0e0fa15d0a2a6082a2f41cf5b/packages/contracts/lib.esm/index.d.ts#L78

In Lesson 10, if we use deployments.get, everything works fine until getting the contract address, since both functions will return this info. The error actually emit when we try to call the createSubscription function.

For MockV3Aggregator logic in Lesson 7, since it's only getting the contract address, ethers.getContract will work.

After figuring this out, I was thinking, if Patrick were to use ethers.getContract on both scripts, I won't be having this query, and won't be noticing the difference, hahaha.

[othaime-en]

Oh yeah, me too. I think it was a good learning moment including both ways and letting us figure out the difference ourselves.