What is a Smart Contract?

Writing and Deploying a smart Contract using Solidity

Ihuoma Anosike's photo
Ihuoma Anosike
·

6 min read

What is a Smart Contract?

Table of contents

In this article, we are going to learn about smart contracts, writing and deploying a smart contract. “Smart contracts” is one of the buzzwords spreading fast in the Web3 ecosystem, it is the soul of Web3.

This is one of the topics that got me excited during the 4week Prep-Phase of the Web3Ladies Mentorship program. If you've come across this term and you do not yet understand what it means “Fear not”, here you are going to learn about what smart contracts are, write and deploy a simple smart contract that greets you.

Let’s goooooo 🚀🚀🚀

Prerequisite

Remix IDE (Integrated Developer Environment) is an online visual IDE for composing solidity smart contracts and Dapp agents. You can also use IDEs like Atom, VSCode, etc to write solidity smart contracts.

What are Smart contracts?

Smart Contracts are small computer programs that are stored and executed on the Ethereum blockchain network. It is a piece of code that can be executed automatically in a deterministic way - This means that they behave exactly as programmed and cannot be changed.

Smart contracts digitize agreements by turning the terms of an agreement into computer code that automatically executes when the contract terms are met.

Let’s take for example when you get insurance for your car and it gets into an accident, you will have to take some documents to the insurance company and start the process of getting the insurance money on your car. This process might drag on for months or years and it can be stressful. But if the insurance was done based on a smart contract code, the smart contract reads through the conditions programmed into it and tries to match it with the information you provided, and if it corresponds it executes the code, and in a matter of minutes you would be getting that insurance money🤑

Importance Of Smart Contracts

Smart contracts are permissionless, trustless, and Immutable.

Permissionless

This means that anyone can write and deploy a smart contract. Two developer-friendly languages that can be used to write smart contracts on the Ethereum blockchain network are Solidity and Vyper.

Trustless

This means that there is no need for a third party or middleman. The conditions are both evaluated and executed by a computer code

Immutable

Once a smart contract code is deployed, it cannot be changed because it is stored on the blockchain.

Writing Our Smart Contract

Now we understand what smart contracts are and why we need a smart contract, it's time to write our smart contract. In this article, we are going to create a simple smart contract that greets the user by their name when the user inputs their name.

Step 1: Writing our Solidity code

Navigate to your Remix IDE, this will set up a default workspace that contains a contract, scripts, and tests folder. Remix - Ethereum IDE - Brave 2022-09-12 17.04.08.png

In your contracts folder create a file Greeter.sol

Add the code below at the very top of your Greeter.sol file

//SPDX-License-Identifier: MIT
pragma solidity >=0.7.0 <0.9.0;

The SPDX-License-Identifier helps define the license of our file. In this tutorial, we wil be using the MIT Opensource license.

The pragma solidity >=0.7.0 <0.9.0 line tells the compiler which version of Solidity it will use when compiling our smart contract. In this tutorial, our smart contract can be compiled with a solidity version that is greater than or equal to version 0.7.0 and less than 0.9.0

Now we define our contract using the contract keyword. It is advised that your contract name and your file name are the same.

contract Greeter {
}

Declare the state variables inside our Greeter contract called name and prefix with a type of string and function visibility of public, the prefix variable should take in a string of “Hello ”. State variables are stored on the blockchain and they can be called multiple times in our smart contract.

string public name;
string public prefix = "Hello ";

Still, in our Greeter contract, we write a “setter” function to set the name variable. The function will have a name of setName and an argument that will take in a type of string and function visibility of public.

function setName(string memory  newName) public{
        name = newName;
}

Declaring a “setter” function in solidity, we use the keyword “function”, followed by the “function name” and “function arguments.”

Finally, we will write a corresponding “getter” function with function visibility of public, a keyword view which specifies that the function will only 'read' data on the blockchain and returns the value type of string A getter function doesn't take any arguments as it's only returning some information from the smart contract.

function getGreeting() public view returns (string memory) {
        return string(abi.encodePacked(prefix, name));
}

In the code snippet above we used a function abi.encodePacked to concatenate the two state variables that we defined - prefix and name. String concatenation in Solidity is NOT straightforward as in other Object Oriented programming languages. Our final code should look like this

//SPDX-License-Identifier: MIT
pragma solidity >=0.7.0 <0.9.0;

contract Greeter {
    string public prefix = "Hello ";
    string public name;

    function setName(string memory  newName) public{
        name = newName;
    }

    function getGreeting() public view returns (string memory) {
        return string(abi.encodePacked(prefix, name));
    }
}

Wow! You just wrote a smart contract all by yourself. You are crushing this

Step 2: Compiling our code

First, click on the “Solidity Compiler icon” on the left pane and ensure that the compiler version is set to a version within the version range specified in our code >=0.7.0 <0.9.0. Remix - Ethereum IDE - Brave 2022-09-13 00.10.27.png

Click the “Compile Greeter.sol” button to compile the code. If the compilation was successful you would see a “green” tick next to the “Solidity Compiler icon”.

Step 3: Deploy our Smart contract

Click on the “Deploy and Run Transaction icon”. We will be deploying our smart contract on a test network.

Smart ContractsBlockchainEthereumSolidity