Receive and fallback functions in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a receive function that accepts Ether.

Blockchain / Solidity

receive() external [1] {}

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

Avirtual

Bexternal

Cpayable

Dview

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to add 'payable' causes the function to reject Ether.

Using 'view' or 'virtual' instead of 'payable' is incorrect.

The receive function must be marked payable to accept Ether.

2fill in blank

medium

Complete the code to declare a fallback function that can receive Ether.

Blockchain / Solidity

fallback() external [1] {}

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

Apayable

Bview

Cpure

Dvirtual

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting 'payable' causes the fallback function to reject Ether.

Using 'view' or 'pure' is invalid for fallback functions that receive Ether.

The fallback function must be marked payable to accept Ether sent without data.

3fill in blank

hard

Fix the error in the fallback function declaration to accept Ether.

Blockchain / Solidity

fallback() external [1] {}

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

Apayable

Bview

Cpure

Dnonpayable

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'view' or 'pure' prevents Ether reception.

Forgetting 'payable' causes runtime errors when sending Ether.

Only payable fallback functions can accept Ether.

4fill in blank

hard

Fill both blanks to create a receive function that logs an event when Ether is received.

Blockchain / Solidity

event Received(address sender, uint amount);

receive() external [1] {
    emit Received(msg.sender, msg.[2]);
}

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

Apayable

Bvalue

Cgas

Dview

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'view' instead of 'payable' prevents receiving Ether.

Using 'msg.gas' instead of 'msg.value' gives wrong data.

The receive function must be payable to accept Ether, and msg.value gives the amount of Ether sent.

5fill in blank

hard

Fill all three blanks to create a fallback function that forwards received Ether to a payable address.

Blockchain / Solidity

fallback() external [1] {
    address payable recipient = payable(msg.sender);
    (bool success, ) = recipient.call{value: msg.[2]([3]);
    require(success, "Transfer failed.");
}

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

Apayable

Bvalue

C""

Dgas

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting 'payable' causes the fallback to reject Ether.

Using 'msg.gas' instead of 'msg.value' sends wrong amount.

Omitting the empty string for calldata causes syntax errors.

The fallback function must be payable to receive Ether. msg.value is the amount sent, and "" represents empty call data.