Mastering Blockchain Programming with Solidity

Using the default fallback function

A Solidity contract may have only one fallback function defined. This is a special function that doesn't have a function name, doesn't take any arguments to the function, and also doesn't return any values from the function. The fallback function is executed when the data in the transaction is empty, as well as when there is no matching function identifier present in the contract.

The fallback function is defined as follows in the contract:

function() external {    //function body}

The fallback function could have any visibility specified, that is, up until Solidity version 0.4.25. However, version 0.5.0 onwards, only external visibility is allowed.

If the fallback function is payable, the contract can receive ...