Emitting events in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an event named Transfer.

Blockchain / Solidity

event [1](address indexed from, address indexed to, uint256 value);

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ATransfer

BLog

CSend

DNotify

Attempts:

3 left

💡 Hint

Common Mistakes

Using a generic name like Log or Notify instead of Transfer.

Forgetting to declare the event.

The event name is Transfer, which is commonly used to log token transfers.

2fill in blank

medium

Complete the code to emit the Transfer event when tokens are sent.

Blockchain / Solidity

emit Transfer([1], to, amount);

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Amsg.sender

Baddress(this)

Cowner

Drecipient

Attempts:

3 left

💡 Hint

Common Mistakes

Using owner or recipient which may not be defined.

Using address(this) which refers to the contract itself.

msg.sender is the address sending the tokens, so it should be the from parameter in the event.

3fill in blank

hard

Fix the error in the event emission code to correctly emit the Approval event.

Blockchain / Solidity

emit Approval(owner, [1], amount);

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Amsg.sender

Brecipient

Cspender

Dto

Attempts:

3 left

💡 Hint

Common Mistakes

Using recipient or to which are not correct for Approval.

Using msg.sender which may not be the spender.

The Approval event requires the spender address as the second argument.

4fill in blank

hard

Fill both blanks to declare and emit a custom event named Deposit with an indexed sender and amount.

Blockchain / Solidity

event [1](address indexed sender, uint256 amount);

function deposit() public payable {
    emit [2](msg.sender, msg.value);
}

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ADeposit

BTransfer

CApproval

DWithdraw

Attempts:

3 left

💡 Hint

Common Mistakes

Using different event names in declaration and emission.

Using standard event names like Transfer instead of Deposit.

The event name is Deposit, so both declaration and emission use the same name.

5fill in blank

hard

Fill all three blanks to declare an event named OwnershipTransferred and emit it with previous and new owner addresses.

Blockchain / Solidity

event [1](address indexed [2], address indexed [3]);

function transferOwnership(address newOwner) public {
    address oldOwner = owner;
    owner = newOwner;
    emit OwnershipTransferred(oldOwner, newOwner);
}

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AOwnershipTransferred

BpreviousOwner

CnewOwner

Downer

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect parameter names like owner instead of previousOwner.

Mismatching event name and emission.

The event is named OwnershipTransferred and the parameters are previousOwner and newOwner as indexed addresses.