As a blockchain developer, you’ll often need to deploy and manage multiple contracts on the Ethereum blockchain. This can be a time-consuming and error-prone process, especially if you need to deploy contracts in a specific order or if you need to update existing contracts.
To streamline the deployment process, you can use migrations and deployment management tools, such as Hardhat’s @hardhat/migrations
module. In this article, we’ll provide a guide for using migrations and deployment management to deploy and update contracts on the Ethereum blockchain.
Prerequisites
Before you begin, you’ll need to install and set up Hardhat. To install Hardhat, you’ll need Node.js and npm. To set up Hardhat, you’ll need to create a hardhat.config.js
file in the root directory of your project.
Migrations
A migration is a script that deploys or updates contracts on the Ethereum blockchain. Migrations are typically used to deploy contracts in a specific order or to update existing contracts.
To use migrations, you’ll need to install the @hardhat/migrations
module and create a migrations
directory in the root directory of your project. You’ll also need to create a 2_deploy_contracts.js
file in the migrations
directory.
The 2_deploy_contracts.js
file should export a migrate
function that takes a deployer
object as an argument. The deployer
object provides methods for deploying and updating contracts.
To deploy a contract, you can use the deploy
method of the deployer
object. For example, to deploy a contract called MyContract
, you can use the following code:
const MyContract = artifacts.require("MyContract");
async function migrate(deployer) {
await deployer.deploy(MyContract);
}
module.exports = migrate;
To update an existing contract, you can use the link
method of the deployer
object. For example, to update a contract called MyLibrary
with a new version, you can use the following code:
const MyLibrary = artifacts.require("MyLibrary");
async function migrate(deployer) {
await deployer.link(MyLibrary, "0x123");
}
module.exports = migrate;
To deploy or update contracts in a specific order, you can use the then
method of the deployer
object. For example, to deploy a contract called MyContract
after a contract called MyLibrary
, you can use the following code:
const MyContract = artifacts.require("MyContract");
const MyLibrary = artifacts.require("MyLibrary");
async function migrate(deployer) {
await deployer.deploy(MyLibrary).then(() => {
return deployer.deploy(MyContract, MyLibrary.address);
});
}
module.exports = migrate;
Deployment Management
To deploy or update contracts using migrations, you can use the `hardhat run` command. For example, to deploy or update all contracts in the `migrations` directory, you can use the following command:
hardhat run migrate
To deploy or update a specific contract, you can use the --migration
option of the hardhat run
command. For example, to deploy or update the MyContract
contract, you can use the following command:
hardhat run migrate --migration 2_deploy_contracts.js
Deployment Strategies
To deploy or update contracts on the Ethereum blockchain, you’ll need to choose a deployment strategy. A deployment strategy is a set of rules that determine how contracts are deployed or updated.
Hardhat supports several deployment strategies, including the following:
deployIfDifferent
: Deploys a contract if it is different from the existing contract.reupload
: Deploys a contract regardless of whether it is different from the existing contract.link
: Links a contract to an existing contract.
To specify a deployment strategy, you can use the strategy
option of the deployer
object. For example, to use the link
deployment strategy, you can use the following code:
const MyContract = artifacts.require("MyContract");
async function migrate(deployer) {
await deployer.deploy(MyContract, { strategy: "link" });
}
module.exports = migrate;
Conclusion
In this article, we provided a guide for using migrations and deployment management to deploy and update contracts on the Ethereum blockchain. By following these steps and using deployment strategies, you can streamline the deployment process and ensure that your contracts are deployed and updated correctly.
Migrations and deployment management are essential tools for any blockchain developer, and they can save you time and reduce the risk of errors when deploying and updating contracts. With the right tools and strategies in place, you can focus on building great blockchain applications, rather than worrying about deployment issues.
Exercises
To review these concepts, we will go through a series of exercises designed to test your understanding and apply what you have learned.
Create a migration that deploys a contract called MyContract
and a contract called MyLibrary
. The MyContract
contract should depend on the MyLibrary
contract, and it should be deployed after the MyLibrary
contract.
const MyContract = artifacts.require("MyContract");
const MyLibrary = artifacts.require("MyLibrary");
async function migrate(deployer) {
await deployer.deploy(MyLibrary).then(() => {
return deployer.deploy(MyContract, MyLibrary.address);
});
}
module.exports = migrate;
Create a migration that updates the MyLibrary
contract with a new version.
const MyLibrary = artifacts.require("MyLibrary");
async function migrate(deployer) {
await deployer.link(MyLibrary, "0x123");
}
module.exports = migrate;
Use the hardhat run
command to deploy or update all contracts in the migrations
directory.
hardhat run migrate
Use the hardhat run
command to deploy or update the MyContract
contract.
hardhat run migrate --migration 2_deploy_contracts.js
Create a migration that deploys a contract called MyContract
using the link
deployment strategy.
const MyContract = artifacts.require("MyContract");
async function migrate(deployer) {
await deployer.deploy(MyContract, { strategy: "link" });
}
module.exports = migrate;