Deploy Uniswap V2

Introduction

Decentralized exchanges (DEXs) are a cornerstone of the DeFi ecosystem, allowing for permissionless token swaps without intermediaries. Uniswap V2, with its Automated Market Maker (AMM) model, revolutionized DEXs by enabling liquidity provision for any ERC-20 token pair.

This tutorial will guide you through how Uniswap V2 works so you can take advantage of it in your projects deployed to Polkadot Hub. By understanding these contracts, you'll gain hands-on experience with one of the most influential DeFi protocols and understand how it functions across blockchain ecosystems.

Prerequisites

Before starting, make sure you have:

• Node.js (v16.0.0 or later) and npm installed
• Basic understanding of Solidity and JavaScript
• Familiarity with hardhat-polkadot development environment
• Some PAS test tokens to cover transaction fees (obtained from the Polkadot faucet)
• Basic understanding of how AMMs and liquidity pools work

Set Up the Project

Let's start by cloning the Uniswap V2 project:

1. Clone the Uniswap V2 repository:

   git clone https://github.com/polkadot-developers/polkavm-hardhat-examples.git -b v0.0.6
   cd polkavm-hardhat-examples/uniswap-v2-polkadot/
   

2. Install the required dependencies:

   npm install
   

3. Update the hardhat.config.js file so the paths for the Substrate node and the ETH-RPC adapter match with the paths on your machine. For more info, check the Testing your Contract section in the Hardhat guide

   hardhat.config.js

   hardhat: {
     polkavm: true,
     nodeConfig: {
       nodeBinaryPath: '../bin/substrate-node',
       rpcPort: 8000,
       dev: true,
     },
     adapterConfig: {
       adapterBinaryPath: '../bin/eth-rpc',
       dev: true,
     },
   },
   

4. Create a .env file in your project root to store your private keys (you can use as an example the env.example file):

   .env

   LOCAL_PRIV_KEY="INSERT_LOCAL_PRIVATE_KEY"
   AH_PRIV_KEY="INSERT_AH_PRIVATE_KEY"
   

   Ensure to replace "INSERT_LOCAL_PRIVATE_KEY" with a private key available in the local environment (you can get them from this file). And "INSERT_AH_PRIVATE_KEY" with the account's private key you want to use to deploy the contracts. You can get this by exporting the private key from your wallet (e.g., MetaMask).

   Warning

   Keep your private key safe, and never share it with anyone. If it is compromised, your funds can be stolen.

5. Compile the contracts:

   npx hardhat compile
   

If the compilation is successful, you should see the following output:

npx hardhat compile Compiling 12 Solidity files Successfully compiled 12 Solidity files

After running the above command, you should see the compiled contracts in the artifacts-pvm directory. This directory contains the ABI and bytecode of your contracts.

Understanding Uniswap V2 Architecture

Before interacting with the contracts, it's essential to understand the core architecture that powers Uniswap V2. This model forms the basis of nearly every modern DEX implementation and operates under automated market making, token pair liquidity pools, and deterministic pricing principles.

At the heart of Uniswap V2 lies a simple but powerful system composed of two major smart contracts:

• Factory Contract - the factory acts as a registry and creator of new trading pairs. When two ERC-20 tokens are to be traded, the Factory contract is responsible for generating a new Pair contract that will manage that specific token pair’s liquidity pool. It keeps track of all deployed pairs and ensures uniqueness—no duplicate pools can exist for the same token combination
• Pair Contract - each pair contract is a decentralized liquidity pool that holds reserves of two ERC-20 tokens. These contracts implement the core logic of the AMM, maintaining a constant product invariant (x * y = k) to facilitate swaps and price determination. Users can contribute tokens to these pools in return for LP (liquidity provider) tokens, which represent their proportional share of the reserves

This minimal architecture enables Uniswap to be highly modular, trustless, and extensible. By distributing responsibilities across these components, developers, and users can engage with the protocol in a composable and predictable manner, making it an ideal foundation for DEX functionality across ecosystems, including Polkadot Hub.

The project scaffolding is as follows:

uniswap-V2-polkadot
├── bin/
├── contracts/
│   ├── interfaces/
│   │   ├── IERC20.sol
│   │   ├── IUniswapV2Callee.sol
│   │   ├── IUniswapV2ERC20.sol
│   │   ├── IUniswapV2Factory.sol
│   │   └── IUniswapV2Pair.sol
│   ├── libraries/
│   │   ├── Math.sol
│   │   ├── SafeMath.sol
│   │   └── UQ112x112.sol
│   ├── test/
│   │   └── ERC20.sol
│   ├── UniswapV2ERC20.sol
│   ├── UniswapV2Factory.sol
│   └── UniswapV2Pair.sol
├── ignition/
├── scripts/
│   └── deploy.js
├── node_modules/
├── test/
│   ├── shared/
│   │   ├── fixtures.js
│   │   └── utilities.js
│   ├── UniswapV2ERC20.js
│   ├── UniswapV2Factory.js
│   └── UniswapV2Pair.js
├── .env.example
├── .gitignore
├── hardhat.config.js
├── package.json
└── README.md

Test the Contracts

You can run the provided test suite to ensure the contracts are working as expected. The tests cover various scenarios, including creating pairs, adding liquidity, and executing swaps.

To test it locally, you can run the following commands:

1. Spawn a local node for testing:

   npx hardhat node
   

   This command will spawn a local Substrate node along with the ETH-RPC adapter. The node will be available at ws://127.0.0.1:8000 and the ETH-RPC adapter at http://localhost:8545.

2. In a new terminal, run the tests:

   npx hardhat test --network localNode
   

The result should look like this:

npx hardhat test --network localNode Compiling 12 Solidity files Successfully compiled 12 Solidity files UniswapV2ERC20 ✔ name, symbol, decimals, totalSupply, balanceOf, DOMAIN_SEPARATOR, PERMIT_TYPEHASH (44ms) ✔ approve (5128ms) ✔ transfer (5133ms) ✔ transfer:fail ✔ transferFrom (6270ms) ✔ transferFrom:max (6306ms) UniswapV2Factory ✔ feeTo, feeToSetter, allPairsLength ✔ createPair (176ms) ✔ createPair:reverse (1224ms) ✔ setFeeTo (1138ms) ✔ setFeeToSetter (1125ms) UniswapV2Pair ✔ mint (11425ms) ✔ getInputPrice:0 (12590ms) ✔ getInputPrice:1 (17600ms) ✔ getInputPrice:2 (17618ms) ✔ getInputPrice:3 (17704ms) ✔ getInputPrice:4 (17649ms) ✔ getInputPrice:5 (17594ms) ✔ getInputPrice:6 (13643ms) ✔ optimistic:0 (17647ms) ✔ optimistic:1 (17946ms) ✔ optimistic:2 (17657ms) ✔ optimistic:3 (21625ms) ✔ swap:token0 (12665ms) ✔ swap:token1 (17631ms) ✔ burn (17690ms) ✔ feeTo:off (23900ms) ✔ feeTo:on (24991ms) 28 passing (12m)

Deploy the Contracts

After successfully testing the contracts, you can deploy them to the local node or Polkadot Hub. The deployment script is located in the scripts directory and is named deploy.js. This script deploys the Factory and Pair contracts to the network.

To deploy the contracts, run the following command:

npx hardhat run scripts/deploy.js --network localNode

This command deploys the contracts to your local blockchain for development and testing. If you want to deploy to Polkadot Hub, you can use the following command:

npx hardhat run scripts/deploy.js --network passetHub

The command above deploys to the actual Polkadot TestNet. It requires PAS test tokens, persists on the network, and operates under real network conditions.

The deployment script will output the addresses of the deployed contracts. Save these addresses, as you will need them to interact with the contracts. For example, the output should look like this:

npx hardhat run scripts/deploy.js --network localNode Successfully compiled 12 Solidity files Deploying contracts using 0xf24FF3a9CF04c71Dbc94D0b566f7A27B94566cac Deploying UniswapV2ERC20... ETH deployed to : 0x7acc1aC65892CF3547b1b0590066FB93199b430D Deploying UniswapV2Factory... Factory deployed to : 0x85b108660f47caDfAB9e0503104C08C1c96e0DA9 Deploying UniswapV2Pair with JsonRpcProvider workaround... Pair deployed to : 0xF0e46847c8bFD122C4b5EEE1D4494FF7C5FC5104

Conclusion

This tutorial guided you through deploying Uniswap V2 contracts to Polkadot Hub. This implementation brings the powerful AMM architecture to the Polkadot ecosystem, laying the foundation for the decentralized trading of ERC-20 token pairs.

By following this guide, you've gained practical experience with:

• Setting up a Hardhat project for deploying to Polkadot Hub
• Understanding the Uniswap V2 architecture
• Testing Uniswap V2 contracts in a local environment
• Deploying contracts to both local and testnet environments

To build on this foundation, you could extend this project by implementing functionality to create liquidity pools, execute token swaps, and build a user interface for interacting with your deployment.

This knowledge can be leveraged to build more complex DeFi applications or to integrate Uniswap V2 functionality into your existing projects on Polkadot.

Last update: June 13, 2025
| Created: June 13, 2025