EVM Smart Contract

Develop and deploy your first Solidity smart contract on Mandala EVM, bridging Ethereum development with the Polkadot ecosystem.

Overview

Mandala Testnet provides full Ethereum Virtual Machine (EVM) compatibility, allowing you to deploy existing Ethereum smart contracts and use familiar tools like Remix, Hardhat, and MetaMask.

EVM Environment Setup

Network Configuration

Mandala EVM Details:

• Network Name: Mandala Testnet EVM
• RPC URL: https://rpc1.paseo.mandalachain.io
• Chain ID: 4818
• Currency: KPGT

MetaMask Configuration

Add Mandala to MetaMask:

1. Open MetaMask → Click network dropdown

2. Select "Add Network" → "Add a custom network"

   

3. Enter network details:

   Field	Value
   Network Name	Metamask Testnet EVM
   New RPC URL	https://rpc1.paseo.mandalachain.io
   Chain ID	4818
   Currency Symbol	KPGT

   

4. Click "Save" and switch to Mandala network

   

   

   

Development Environment

Tool Options

Choose your preferred development environment:

Option 1: Remix IDE (Recommended for beginners)

• Browser-based, no installation required
• Built-in compiler and debugger
• Direct deployment to networks

Remix IDE Setup

Accessing Remix:

1. Visit: https://remix.ethereum.org
2. Accept privacy policy and close welcome screen
3. Open file in contracts folder: Storage.sol

Building Your First Contract

Storage Contract

Create a basic contract that stores and retrieves a number:

// SPDX-License-Identifier: GPL-3.0

pragma solidity >=0.8.2 <0.9.0;

/**
 * @title Storage
 * @dev Store & retrieve value in a variable
 * @custom:dev-run-script ./scripts/deploy_with_ethers.ts
 */
contract Storage {

    uint256 number;

    /**
     * @dev Store value in variable
     * @param num value to store
     */
    function store(uint256 num) public {
        number = num;
    }

    /**
     * @dev Return value 
     * @return value of 'number'
     */
    function retrieve() public view returns (uint256){
        return number;
    }
}

Contract Features

Key Components:

State Variables:

uint256 number;  // Public storage variable for storing a number

Functions:

• store(uint256 num) - Store a value in the number variable
• retrieve() - Read and return the stored number value

Function Details:

Store Function:

function store(uint256 num) public {
    number = num;
}

• Visibility: Public (can be called by anyone)
• Purpose: Updates the stored number with a new value
• Parameter: num - the new value to store

Retrieve Function:

function retrieve() public view returns (uint256){
    return number;
}

• Visibility: Public view (read-only, doesn't modify state)
• Purpose: Returns the currently stored number
• Returns: The value stored in the number variable

Compiling the Contract

Using Remix

1. Select Solidity Compiler tab (left sidebar)

2. Choose compiler version: 0.8.19 or later

3. Enable optimization (optional)

4. Click "Compile Storage.sol"

   

Compilation artifacts:

• Bytecode: Contract's compiled code
• ABI: Application Binary Interface
• Metadata: Contract information

Deploying to Mandala

Remix Deployment

1. Go to "Deploy & Run Transactions" tab

2. Set environment to "Injected Provider - MetaMask"

3. Verify network shows "Mandala Testnet EVM (4818)"

4. Select Storage contract

5. Click "Deploy"

   

MetaMask Transaction

1. MetaMask popup will show transaction details

2. Review gas fee and contract creation

3. Click "Confirm" to deploy

4. Wait for confirmation (usually 12-24 seconds)

   

Deployment Success

After successful deployment:

• Contract address is generated (0x...)

• Contract appears in Remix deployed contracts

• Transaction hash is provided

• Gas used is displayed

  

• On metamask Activity section will show the Contract deployment as well

  

Interacting with Your Contract

Using the Deployed Contract

Once deployed, you can interact with your Storage contract:

Storing a Value:

1. In the deployed contracts section, find your Storage contract
2. Expand the contract to see available functions
3. Enter a number in the store function input field
4. Click the store button
5. Confirm the transaction in MetaMask

Retrieving the Value:

1. Click the retrieve button (no input needed)
2. The stored number will be displayed immediately
3. This is a view function, so no gas is required

Security Best Practices

Common Vulnerabilities

Reentrancy protection:

import "@openzeppelin/contracts/security/ReentrancyGuard.sol";

contract SecureContract is ReentrancyGuard {
    function withdraw() public nonReentrant {
        // Safe withdrawal logic
    }
}

Integer overflow protection:

// Use SafeMath or Solidity ^0.8.0 built-in checks
function safeAdd(uint256 a, uint256 b) public pure returns (uint256) {
    return a + b;  // Automatically checks for overflow
}

Access control:

import "@openzeppelin/contracts/access/Ownable.sol";

contract ControlledContract is Ownable {
    function sensitiveFunction() public onlyOwner {
        // Only owner can call
    }
}

Additional Resources:

• Solidity Documentation
• OpenZeppelin Contracts
• Ethereum Development Best Practices

Congratulations! You've successfully deployed your first EVM smart contract on Mandala Testnet, demonstrating the power of Polkadot's multi-virtual machine architecture!