#Modifying an existing module

If you have defined your modules and deployed them, you can still modify them.

If we wanted to add a new Rocket to the module we deployed in the Quick Start guide, all we need to do is modifying the module definition like this

TypeScript

JavaScript

ignition/modules/Apollo.ts

import { buildModule } from "@nomicfoundation/hardhat-ignition/modules";

export default buildModule("Apollo", (m) => {
  const apollo = m.contract("Rocket", ["Apollo"]);

  m.call(apollo, "launch", []);

  const starship = m.contract("Rocket", ["Starship"], { id: "starship" });

  m.call(starship, "launch", []);

  return { apollo, starship };
});

ignition/modules/Apollo.js

const { buildModule } = require("@nomicfoundation/hardhat-ignition/modules");

module.exports = buildModule("Apollo", (m) => {
  const apollo = m.contract("Rocket", ["Apollo"]);

  m.call(apollo, "launch", []);

  const starship = m.contract("Rocket", ["Starship"], { id: "starship" });

  m.call(starship, "launch", []);

  return { apollo, starship };
});

Then, we can run it just like the first time, and Hardhat Ignition will continue from where it left

TypeScript

JavaScript

npx hardhat ignition deploy ignition/modules/Apollo.ts --network localhost

npx hardhat ignition deploy ignition/modules/Apollo.js --network localhost

and we'll get a result like this

Batch #1
  Executed Apollo#starship

Batch #2
  Executed Apollo#Apollo.starship.launch


[ Apollo ] successfully deployed 🚀

Deployed Addresses

Apollo#Rocket - 0x5fbdb2315678afecb367f032d93f642f64180aa3
Apollo#starship - 0x9fe46736679d2d9a65f0992f2272de9f3c7fa6e0

with two new batches, that execute the new parts of the module, while keeping the previous results.

# Incompatible modifications

If you try to modify the definition of a Future that has already been partially or completely executed in an incompatible way, it may not be possible to resume your existing deployment. To learn more about this, please read the Reconciliation guide.