Chapter 9 of 9

Putting it all online on the test network

So far you have worked locally. Deploying means sending the compiled code to the network: the contract gets an address and from then on is visible to everyone. You do it with Hardhat, a development environment for contracts.

// hardhat.config.ts (extract)
networks: {
  amoy: {
    url: "https://polygon-amoy-bor-rpc.publicnode.com",
    chainId: 80002,
    accounts: [process.env.DEPLOYER_PRIVATE_KEY],
  },
},

// scripts/deploy.ts (extract)
const oracle = await ethers.deployContract("FuelPriceOracle", [deployer.address]);
await oracle.waitForDeployment();
const token = await ethers.deployContract("FuelToken", [await oracle.getAddress()]);
await token.waitForDeployment();
await oracle.grantRole(await oracle.UPDATER_ROLE(), UPDATER_ADDRESS);

• networks.amoy tells Hardhat where to publish: RPC address and Chain ID 80002.
• accounts uses the deployer key taken from the environment: a fresh test key, never a real one.
• deployContract publishes the oracle first, then the token, passing it the oracle's address.
• The last line gives the updater address (the chapter 7 program) the role that lets it write prices.

Checklist

1. Create two test keys: one to deploy, one to update prices. Never reuse real keys.
2. Get test POL for both from the chapter 3 faucets.
3. Put the variables in the .env file (never shared or uploaded to GitHub): the deployer key, the updater address, and a Polygonscan API key for step 6.
4. Deploy with npx hardhat run scripts/deploy.ts --network amoy and note the two addresses.
5. Configure the chapter 7 program with the oracle address and the updater key, then run it once.
6. Verify on Polygonscan (amoy.polygonscan.com): verification publishes the source code next to the contract, so anyone can read what is really running.
7. Check: the oracle shows today's prices and date, and isFresh(259200) answers true (259,200 seconds are 3 days).
8. Try a purchase of 0.1 POL from the web page and look at the transaction in the explorer.

If a purchase fails with "old price", the oracle is not fresh: run the chapter 7 program again.

One last tip: do a full run on Hardhat's local network first (npx hardhat node), where mistakes cost nothing and everything is fast.

Going deeper

• Hardhat: documentation
• Polygon documentation