Factory pattern in Blockchain / Solidity - Mini Project: Build & Apply

Factory Pattern in Blockchain Smart Contracts

📖 Scenario: You are working on a blockchain project where you need to create multiple simple contracts that represent digital assets. Instead of deploying each contract manually, you will build a factory contract that can create new asset contracts on demand.

🎯 Goal: Build a factory contract in Solidity that can create new asset contracts. Each asset contract will store a name and an owner address. The factory will keep track of all created asset contracts.

📋 What You'll Learn

Create a simple asset contract with a name and owner state variables.

Create a factory contract that can deploy new asset contracts.

Store the addresses of all created asset contracts in the factory.

Provide a function to get the total number of created asset contracts.

💡 Why This Matters

🌍 Real World

Factory patterns are used in blockchain to efficiently deploy many similar contracts, such as tokens, NFTs, or digital assets, without manual deployment each time.

💼 Career

Understanding factory patterns is important for blockchain developers to write scalable and maintainable smart contracts that manage multiple contract instances.

1

Create the Asset Contract

Write a Solidity contract called Asset with two public state variables: string public name and address public owner. Add a constructor that takes string memory _name and address _owner as parameters and sets the state variables accordingly.

Blockchain / Solidity

// Your code here

Need a hint?

Think of the asset contract as a simple container that stores a name and an owner address. The constructor sets these values when the contract is created.

2

Create the Factory Contract with Storage

Write a Solidity contract called AssetFactory. Inside it, create a public dynamic array of addresses called assets to store the addresses of created asset contracts.

Blockchain / Solidity

pragma solidity ^0.8.0;

contract Asset {
    string public name;
    address public owner;

    constructor(string memory _name, address _owner) {
        name = _name;
        owner = _owner;
    }
}

contract AssetFactory {
    // Your code here
}

Need a hint?

The factory contract will keep track of all asset contracts it creates by storing their addresses in an array.

3

Add Function to Create New Asset Contracts

Inside the AssetFactory contract, add a public function called createAsset that takes a string memory _name parameter. This function should deploy a new Asset contract with _name and msg.sender as the owner. Then, add the new asset's address to the assets array.

Blockchain / Solidity

pragma solidity ^0.8.0;

contract Asset {
    string public name;
    address public owner;

    constructor(string memory _name, address _owner) {
        name = _name;
        owner = _owner;
    }
}

contract AssetFactory {
    address[] public assets;

    // Add createAsset function here
}

Need a hint?

Use the new keyword to deploy a new contract inside another contract. Store the new contract's address in the array.

4

Add Function to Get Total Number of Assets and Test

Add a public view function called getAssetsCount in the AssetFactory contract that returns the number of created asset contracts. Then, write a simple test by calling createAsset twice with names "Gold" and "Silver", and print the result of getAssetsCount().

Blockchain / Solidity

pragma solidity ^0.8.0;

contract Asset {
    string public name;
    address public owner;

    constructor(string memory _name, address _owner) {
        name = _name;
        owner = _owner;
    }
}

contract AssetFactory {
    address[] public assets;

    function createAsset(string memory _name) public {
        Asset newAsset = new Asset(_name, msg.sender);
        assets.push(address(newAsset));
    }

    // Add getAssetsCount function here
    // Then test by creating two assets and printing the count
}

Need a hint?

The length of the assets array tells how many asset contracts have been created. Solidity contracts do not print, so you return values to check.