Solidity Tutorial: all about Functions

Table of Contents

Function visibility

View vs Pure

Named Arguments in Functions

Payable functions

Fallback functions

Receive functions

Functions overloading

Functions signature

External functions

Recursive Functions : preventing re-entrancy

Function Visibility

Introduction

Solidity is a high level language for the EVM. The EVM under the hood does what we call EVM calls, known as “message calls”. From a higher perspective, Solidity knows two kind of function calls:

• internal ones: do not create an EVM call
• external ones: create an EVM call

4 visibilities availables

There are 4 main visibilities that can be assigned to functions in Solidity.

Let’s look at them in more details:

public : visible everywhere (within the contract itself and other contracts or addresses).

Therefore, it is part of the contract interface (ABI). It can be called internally or via messages.

private : visible only by the contract it is defined in, not derived contracts.

These functions are not part of the contract interface (ABI).

NB: Everything that is inside a contract is visible to all observers external to the blockchain. Making something private only prevents other contracts from reading or modifying the information, but it will still be visible to the whole world outside of the blockchain.