Overview
The SimpleStorage contract demonstrates basic Solidity concepts including state variables, structs, arrays, mappings, and functions. This contract allows users to store and retrieve a favorite number, as well as maintain a list of people with their associated favorite numbers.
Contract Details
- Solidity Version: 0.8.30
- License: MIT
State Variables
Stores the favorite number. Initialized to 3 by default.
A dynamic array that stores all Person structs added to the contract.
nameToNumber
mapping(string => uint256)
Maps a person’s name to their favorite number for quick lookup.
Structs
Person
A struct representing a person with their favorite number.
The person’s favorite number.
Functions
store
function store(uint256 _favoriteNumber) public
The new favorite number to store.
myFavoriteNumber
retrieve
function retrieve() public view returns (uint256)
myFavoriteNumber
Access: Public
Modifiers: view (read-only, does not modify state)
addPerson
function addPerson(string memory _name, uint256 _favoriteNumber) public
The name of the person to add.
The person’s favorite number.
- Adds a new Person struct to
listOfPeople
- Creates/updates an entry in
nameToNumber mapping
listOfPeople (getter)
function listOfPeople(uint256 index) public view returns (Person)
listOfPeople array.
The index of the person in the array.
view (read-only)
nameToNumber (getter)
function nameToNumber(string memory name) public view returns (uint256)
nameToNumber mapping.
Returns: The favorite number associated with the given name
Access: Public
Modifiers: view (read-only)
Complete Source Code
// SPDX-License-Identifier: MIT
pragma solidity 0.8.30;
contract SimpleStorage {
uint256 myFavoriteNumber = 3;
//uint256[] listOfFavoriteNumbers;
struct Person {
uint256 favoriteNumber;
string name;
}
// Person public pat = Person(7, "Pat");
Person[] public listOfPeople;
mapping(string => uint256) public nameToNumber;
function store(uint256 _favoriteNumber) public {
myFavoriteNumber = _favoriteNumber;
}
function retrieve() public view returns (uint256) {
return myFavoriteNumber;
}
function addPerson(string memory _name, uint256 _favoriteNumber) public {
listOfPeople.push(Person(_favoriteNumber, _name));
nameToNumber[_name] = _favoriteNumber;
}
}
Usage Examples
Storing a Favorite Number
// Store the number 42 as the favorite number
simpleStorage.store(42);
Retrieving the Favorite Number
// Get the current favorite number
uint256 currentFavorite = simpleStorage.retrieve();
Adding a Person
// Add a person named "Alice" with favorite number 7
simpleStorage.addPerson("Alice", 7);
Looking Up by Name
// Get Alice's favorite number
uint256 aliceFavorite = simpleStorage.nameToNumber("Alice");
Accessing the People List
// Get the first person in the list
Person memory firstPerson = simpleStorage.listOfPeople(0);