April 27, 2024

SimpleStorage: Your First Smart Contract

5 min readSmart Contracts

The SimpleStorage contract is often the first smart contract that developers write when learning Solidity. It demonstrates fundamental concepts like state variables, functions, and storage while remaining easy to understand.

Contract Overview

This contract does exactly what its name suggests: it stores a number on the blockchain. While simple, it introduces several key concepts that are essential for understanding smart contracts:

State variables and storage
Public variables and getter functions
Function visibility and modifiers
Basic contract interaction

The Contract

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

contract SimpleStorage {
    uint public storedNumber;

    // Store a number
    function set(uint _num) public {
        storedNumber = _num;
    }

    // Retrieve the stored number
    function get() public view returns (uint) {
        return storedNumber;
    }
}

Breaking It Down

1. License and Version

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

Every Solidity file should start with a license identifier and a pragma directive. The pragma specifies which Solidity version to use (^0.8.20 means "0.8.20 or higher, but less than 0.9.0").

2. State Variable

uint public storedNumber;

This line declares a state variable that will be stored on the blockchain:

uint: An unsigned integer (can only store positive numbers)
public: Automatically creates a getter function
storedNumber: The name of our variable

3. Set Function

function set(uint _num) public {
    storedNumber = _num;
}

This function allows anyone to update the stored number:

public: Makes the function callable by anyone
uint _num: Takes a number as input
Updates the state variable with the new value

4. Get Function

function get() public view returns (uint) {
    return storedNumber;
}

This function retrieves the stored number:

view: Indicates this function doesn't modify state
returns (uint): Specifies the return type
Note: This function is actually redundant since we made storedNumber public

Key Concepts

State Variables

Variables declared outside functions are stored on the blockchain. They persist between transactions and cost gas to modify.

Function Visibility

public functions can be called by anyone. Other options include private, internal, and external.

View Functions

Functions marked as view don't modify state and are free to call (they don't require a transaction).

Public Variables

When a state variable is declared as public, Solidity automatically generates a getter function for it.

Next Steps

While this contract is simple, it's a great foundation for learning more complex concepts:

Add access control to restrict who can set the number
Store multiple numbers using arrays or mappings
Add events to track changes
Implement more complex data structures

#SmartContracts #Solidity #Ethereum #Web3 #Blockchain #Development #Tutorial

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