Monitoring deployed contracts in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to fetch the contract address after deployment.

Blockchain / Solidity

const contractAddress = deployedContract.[1];

Drag options to blanks, or click blank then click option'

AgetAddress

Baddress

CcontractAddress

Daddr

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method instead of a property

Using incorrect property names like 'addr' or 'contractAddress'

The deployed contract object has an address property that stores the contract's address on the blockchain.

2fill in blank

medium

Complete the code to listen for the 'Transfer' event emitted by the contract.

Blockchain / Solidity

contract.on('[1]', (from, to, amount) => { console.log(`Transfer from ${from} to ${to} of ${amount}`); });

Drag options to blanks, or click blank then click option'

AApproval

BWithdraw

CDeposit

DTransfer

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong event names like 'Deposit' or 'Withdraw'

Confusing event names with method names

The 'Transfer' event is commonly emitted when tokens move between addresses. Listening to it helps monitor contract activity.

3fill in blank

hard

Fix the error in the code to correctly fetch the transaction receipt after deployment.

Blockchain / Solidity

const receipt = await provider.getTransaction[1](txHash);

Drag options to blanks, or click blank then click option'

AReceiptSync

BReceiptAsync

CReceipt

DReceipts

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect method names like 'getTransactionReceipts' or adding 'Async' suffix

Misspelling 'Receipt'

The correct method to get a transaction receipt is getTransactionReceipt. It returns details about the transaction's success and events.

4fill in blank

hard

Fill both blanks to create a filter for monitoring events from a specific contract address and event name.

Blockchain / Solidity

const filter = { address: '[1]', topics: [ethers.utils.id('[2]')] };

Drag options to blanks, or click blank then click option'

A0xAbC1234567890defABC1234567890DEFabc12345

BTransfer(address,address,uint256)

CApproval(address,address,uint256)

D0x0000000000000000000000000000000000000000

Attempts:

3 left

💡 Hint

Common Mistakes

Using zero address instead of contract address

Using wrong event signature like 'Approval' when monitoring transfers

The filter requires the contract's address and the event signature hashed as a topic. 'Transfer(address,address,uint256)' is the event signature for token transfers.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps event names to their decoded data if the event matches a filter.

Blockchain / Solidity

const decodedEvents = events.reduce((acc, event) => { if(event.event === '[1]') { acc[event.event] = [2].[3](event.data); } return acc; }, {});

Drag options to blanks, or click blank then click option'

ATransfer

BcontractInterface

CdecodeEventLog

DApproval

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong event names like 'Approval'

Calling non-existent methods on the interface

Not matching event names correctly

This code checks if the event is 'Transfer', then uses the contract interface's decodeEventLog method to decode the event data and store it in a dictionary.