Solidity Tutorial : all about Constructors

This article covers constructors, a function in Solidity that runs only once, when the contract is deployed onto the Ethereum network.

Table of Contents

Introduction

How to define a constructor

Public vs Internal Constructors

Constructors’ parameters and inheritance

Payable Constructor

Introduction

Constructors are a common concept in OOP. In many programming languages, when defining classes, you can also define a magic method that will run once, at the time a new instance of the object is created.

In the case of Solidity, the code defined inside the constructor will run only once, at the time the contract is created and deployed in the network.

An important point to mention is the following:

The bytecode deployed on the network does not contain the constructor code, since the constructor code runs only once on deployment.

OpenZeppelin explains the idea more precisely in the second part of their article…