🚀Deploying Your Contract

Ready to write a smart contract, interact with it and finally deploy & verify it?

Tip: If you have not watched the first video, go back to Installation & Setup to understand how to set up your Celo composer environment and understand its folder structure.

Goal

We are going to write our first smart contract with Celo-composer. Our smart contract will be a simple mintable ERC20 token that is also pausable by the token owner which is you then we will go ahead to verify our smart contract on the Celo testnet Alfajores. Ready? Let's Go 👟

Visit OpenZeppelin Contract Wizard

Open https://docs.openzeppelin.com/contracts/4.x/wizard in your browser. You will see the contract wizard with the ERC20 token contract as default, next do the following:

• Change the Name field to CeloCommunityToken

• Change the symbol field to CCT

• In the pre-mint field enter 1000. (This will pre-mint 1000 CCT tokens to your address)

• In the Features check on Mintable and Pausable (It's adds minting and pausing functionality)

You should be looking at something like this by now

Create the CeloCommunityToken.sol

Now go back to your code editor, open packages/hardhat/contracts and create a CeloCommunityToken.sol file. Copy the code from the wizard and paste inside the newly created file.

Now cd from your terminal back to packages/hardhat install the Openzeppelin library that our smart contract is importing from.

Run: code

yarn add @openzeppelin/contracts -D

This will install the open Openzeppelin library, you can check your node_modules folder if you would like to inspect the library and browse its code.

Finally, add an extra modifier to the mint function. Just after onlyOwner modifier add whenNotPaused modifier.

Add Deploy Script

Open src/hardhat/contracts/deploy/00-deploy.js and update it with the belwo snippet.

  await deploy("CeloCommunityToken", {
    from: deployer,bas
    log: true,
  });

Next, update the export to include CeloCommunityToken so it can match below.

module.exports.tags = [
  "Greeter",
  "Storage",
  "SupportToken",
  "CeloCommunityToken",
];

And finally, in your root folder, run the below command to deploy your newly added smart contract.

PRIVATE_KEY={YOUR_PRIVATE_KEY_HERE} yarn hardhat:deploy

Above you would see our contract is now being deployed to address 0x2204d0117327A***** . Your own address will differ from mine, and so is everyone else. Hold down the cmd/ctrl and click on tx in your terminal, it will open up the transaction details page on Celo Alfajores explorer using the transaction hash to search.

As you can see in the image above, our new contract was created and immediately minted 1,000 CCT tokens to our address. To view this balance, open your Metamask, click import tokens then copy the smart contract address and paste it into the field that says Token Contract Address the rest will auto fill itself.

Now you should see your 1,000 CCT token balance.

Interact with Contract UI

Celo composer comes with a contract component that allows you call and transact with the functions of the smart contract without having to write a single line of code. If you don't have your react app front end included in Celo composer running by now, in a new terminal on the celo composer project root directory run:

yarn react-app:dev

Open http://localhost:3000 on your browser and click on the CeloCommunnityToken tab, you will see all of the public functions of the smart contracts that you can execute.

• The functions marked view are readonly functions that don't cost us gas fees.

• The non payable functions make changes to the contract states but are not payable i.e. do not direct accept CELO if you send it to them.

• The functions marked payable are state-changing functions and require that yous end CELO to them while calling it.

View functions have call buttons while state-changing functions such as payable and non payable ones have buttons called transact.

Perform the following tasks:

• Call the name (view) function. what does it return?

• Call the balanceOf (view) function and pass your Metamask Account 1 wallet address to it. What does it return?

• Click on owner (view) function. Do you see your Account 1 wallet address returned?

• Open Metamask, create Account 2 following the image below

• Copy the address of Account 2. and paste it inside the to input field of the new token and in the amount paste this 1000000000000000000000. Check the CCT balance of Account 2, if you can't view it import the contract token again to view it. Do you see 1000 CCT minted for the account?

• Call the balanceOf (view) function and pass your Metamask Account 1 wallet address to it. What does it return?

• Open your browser console and open the javascript console tab.

• Click on pause function, and after the transaction, succeeds. Try to mint some tokens again for Account 2 by following the previous step. You will notice it will fail with details logged in the console and when you inspect closely it will show you the reason as Pausable: paused. This was because of the whennotPaused modifier that only allows us to call the function when the contract is not paused. This is usually used as a security measure in case the contract was compromised.

• Click on unpause function and approve the Metamask transaction and everything should be back to normal.