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🔍 Call Functions & Verify Results

Interact with your deployed contract and confirm transactions on-chain

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Introduction

Writing Contract

Compilation & Deployment

Interaction & Verification

Key Takeaways

←

Compilation & Deployment

🔗 Interaction & Verification

Your contract is deployed! Now let's interact with it—read data, write data, and verify the source code on Etherscan.

🎮 Interactive: Contract Interaction Simulator

Choose an action to see how to interact with your deployed contract

📖

Read Data (Free)

Call storedData() to read the current value

Gas Cost: FREE

Steps to Read Data (Free):

Click on "storedData" button in Remix

Function executes locally (no transaction)

View returns current value instantly

No gas cost, no waiting

Code Example:

// Read value (free call)
const value = await contract.storedData()
console.log(value) // Current stored number

📖 Read vs ✏️ Write Operations

📖

Read Operations (Calls)

✅ FREE - No gas cost

✅ Instant - No waiting

✅ No Transaction - Executes locally

✅ View Functions - Only read state

contract.storedData() // FREE

✏️

Write Operations (Transactions)

⚠️ Costs Gas - Pay for computation

⏳ Wait ~15s - Block confirmation

📝 Creates Transaction - Broadcasted to network

🔄 Modifies State - Changes blockchain

contract.set(42) // ~25K gas

🔍 Using Etherscan to Interact

Etherscan provides a user-friendly interface to interact with any contract—no code required!

Step 1: Find Your Contract

Go to sepolia.etherscan.io and paste your contract address

Step 2: Navigate to "Read Contract"

Click the "Contract" tab → "Read Contract" to view all view functions

Step 3: Call storedData()

Click "storedData" to see current value. No wallet connection needed!

Step 4: Navigate to "Write Contract"

Click "Write Contract" → Connect MetaMask when prompted

Step 5: Call set()

Enter value → Click "Write" → Confirm in MetaMask → Wait for confirmation

✅ Why Verify Your Contract?

🔓

Transparency

Anyone can read source code and verify what the contract does

🛡️

Trust

Users can audit logic and confirm no hidden malicious code

🧰

Better UX

Etherscan shows function names instead of raw bytecode

📊

Analytics

Track contract usage, events, and transactions easily

🔗 Interacting with Web3.js

For dApp developers, here's how to interact programmatically:

import { ethers } from 'ethers'

// Connect to wallet
const provider = new ethers.BrowserProvider(window.ethereum)
const signer = await provider.getSigner()

// Contract instance
const contract = new ethers.Contract(
  '0x742d35Cc6634C0532925a3b844Bc9e7595f0bEb', // Address
  ['function set(uint256 x)', 'function storedData() view returns (uint256)'], // ABI
  signer
)

// Read value (free)
const value = await contract.storedData()
console.log('Stored value:', value)

// Write value (costs gas)
const tx = await contract.set(123)
await tx.wait() // Wait for confirmation
console.log('New value set to 123!')

⚠️ Common Pitfalls

❌

Calling Write Functions Without Gas

Always ensure wallet has testnet ETH before calling state-changing functions!

❌

Not Waiting for Confirmation

Always use await tx.wait() to ensure transaction is mined

❌

Wrong Network

Double-check MetaMask is on correct network (Sepolia for testnet)

❌

Incorrect ABI

Use exact ABI from compilation output—function signatures must match!

🎯 Next Steps

1️⃣

Try Different Values: Set 999, 0, 123456 and read them back

2️⃣

Check Transactions: View all transactions on Etherscan

3️⃣

Share Address: Let friends interact with YOUR contract!

4️⃣

Build a dApp: Create a web interface with Web3.js/Ethers.js