Receive and fallback functions in Blockchain / Solidity - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the receive function in a smart contract?

The receive function is a special function in Solidity that is executed when the contract receives plain Ether without any data. It allows the contract to accept Ether transfers.

beginner

When is the fallback function triggered in a smart contract?

The fallback function is called when a contract receives a call with data that does not match any function signature or when Ether is sent but no receive function is defined or if the receive function is not payable.

intermediate

Can a contract have both receive and fallback functions? What happens if both exist?

Yes, a contract can have both. The receive function handles plain Ether transfers with empty calldata, while the fallback function handles calls with data or Ether transfers when receive is not present or not payable.

beginner

What visibility and modifiers must the receive function have?

The receive function must be declared as external and payable to accept Ether transfers.

beginner

What happens if a contract does not have a receive or fallback function and it receives Ether?

The transaction will fail and revert because the contract cannot accept Ether without a receive or fallback function marked payable.

Which function is called when a contract receives Ether with empty calldata?

A constructor()

B fallback()

C payable()

D receive()

The receive() function is triggered when Ether is sent with empty calldata.

What visibility must the fallback function have?

A external

B internal

C private

D public

The fallback function must be declared external.

If a contract has both receive() and fallback(), which handles calls with data?

A receive()

B fallback()

C Both equally

D Neither

fallback() handles calls with data or unknown function signatures.

What happens if a contract without receive() or fallback() receives Ether?

A Ether is stored in fallback

B Ether is accepted silently

C Transaction reverts

D Contract self-destructs

Without receive() or payable fallback(), Ether transfers fail and revert.

Which modifier must be used on receive() to accept Ether?

A payable

B view

C pure

D virtual

The receive() function must be payable to accept Ether.

Explain the difference between the receive() and fallback() functions in Solidity.

Think about when each function is triggered based on the data sent.

Describe what happens when a contract without receive() or fallback() functions receives Ether.

Consider the contract's ability to accept Ether without special functions.