Introduction
Systems for buying movie ticket faces numerous challenges, including high fees, lack of transparency, and limited access. The objective of this proposal is to build a decentralized platform that addresses these issues and enables seamless movie ticket purchases.
Traditional centralized ticketing systems suffer from inefficiencies and security concerns. High fees, lack of transparency, and limited scalability pose significant drawbacks. Security risks and data breaches can compromise user information.
To overcome these challenges, I propose a decentralized architecture powered by Celo blockchain. Smart contracts will automate ticket purchases, reducing fraud and enabling peer-to-peer transactions. Tokenization will facilitate transferability, secondary markets, and loyalty programs.
Prerequisites
To follow along with this tutorial, you should have a basic understanding of Solidity and smart contracts.
You should also have an environment set up to deploy and interact with smart contracts such as Remix IDE
SmartContract
Open your Remix IDE to begin writing this smart contract code
Complete code;
// SPDX-License-Identifier: MIT
pragma solidity >=0.7.0 <0.9.0;
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
contract Movietickets is Ownable {
struct Movieticket {
address payable admin;
string name;
string image;
string filmIndustry;
string genre;
string description;
uint price;
uint sold;
uint ticketsAvailable;
bool forSale;
}
uint internal moviesLength = 0;
address internal cUsdTokenAddress = 0x874069Fa1Eb16D44d622F2e0Ca25eeA172369bC1;
mapping (uint => Movieticket) internal movies;
mapping (address => mapping (uint => uint)) internal userTickets;
uint internal totalRevenue = 0;
event TicketPurchase(address indexed buyer, uint indexed movieIndex, uint ticketCount);
event TicketRefund(address indexed buyer, uint indexed movieIndex, uint ticketCount);
modifier isTicketAvailable(uint _index, uint _tickets) {
require(movies[_index].ticketsAvailable >= _tickets, "Tickets not sufficient");
_;
}
modifier isTicketForSale(uint _index) {
require(movies[_index].forSale == true, "Ticket is not for sale");
_;
}
modifier isAdmin(uint _index) {
require(msg.sender == movies[_index].admin, "Only admin");
_;
}
function addMovie(
string memory _name,
string memory _image,
string memory _filmIndustry,
string memory _genre,
string memory _description,
uint _price,
uint _ticketsAvailable
) public onlyOwner {
uint _sold = 0;
movies[moviesLength] = Movieticket(
payable(msg.sender),
_name,
_image,
_filmIndustry,
_genre,
_description,
_price,
_sold,
_ticketsAvailable,
true
);
moviesLength++;
}
function getMovieTicket(uint _index) public view returns (
address payable,
string memory,
string memory,
string memory,
string memory,
string memory,
uint,
uint,
uint,
bool
) {
Movieticket memory m = movies[_index];
return (
m.admin,
m.name,
m.image,
m.filmIndustry,
m.genre,
m.description,
m.price,
m.sold,
m.ticketsAvailable,
m.forSale
);
}
function addTickets(uint _index, uint _tickets) external isAdmin(_index) {
require(_tickets > 0, "Number of tickets must be greater than zero");
movies[_index].ticketsAvailable += _tickets;
}
function changeForSale(uint _index) external isAdmin(_index) {
movies[_index].forSale = !movies[_index].forSale;
}
function removeTicket(uint _index) external isAdmin(_index) {
movies[_index] = movies[moviesLength - 1];
delete movies[moviesLength - 1];
moviesLength--;
}
function blockTickets(uint _index, uint _tickets) external isAdmin(_index) isTicketAvailable(_index, _tickets) {
movies[_index].ticketsAvailable -= _tickets;
}
function buyBulkMovieTicket(uint _index, uint _tickets
) external payable isTicketForSale(_index) isTicketAvailable(_index, _tickets) {
require(msg.sender != movies[_index].admin, "Admin cannot buy tickets");
require(
IERC20(cUsdTokenAddress).transferFrom(
msg.sender,
movies[_index].admin,
movies[_index].price * _tickets
),
"Transfer failed."
); movies[_index].sold += _tickets;
movies[_index].ticketsAvailable -= _tickets;
userTickets[msg.sender][_index] += _tickets;
totalRevenue += movies[_index].price * _tickets;
emit TicketPurchase(msg.sender, _index, _tickets);
}
function buyMovieTicket(uint _index) public payable isTicketForSale(_index) isTicketAvailable(_index, 1) {
require(msg.sender != movies[_index].admin, "Admin cannot buy tickets");
require(
IERC20(cUsdTokenAddress).transferFrom(
msg.sender,
movies[_index].admin,
movies[_index].price
),
"Transfer failed."
);
movies[_index].sold += 1;
movies[_index].ticketsAvailable -= 1;
userTickets[msg.sender][_index] += 1;
totalRevenue += movies[_index].price;
emit TicketPurchase(msg.sender, _index, 1);
}
function refundTickets(uint _index, uint _tickets) external {
require(_tickets > 0, "Number of tickets must be greater than zero");
require(userTickets[msg.sender][_index] >= _tickets, "Insufficient tickets for refund");
uint refundAmount = movies[_index].price * _tickets;
require(
IERC20(cUsdTokenAddress).transferFrom(
movies[_index].admin,
msg.sender,
refundAmount
),
"Transfer failed."
);
movies[_index].sold -= _tickets;
movies[_index].ticketsAvailable += _tickets;
userTickets[msg.sender][_index] -= _tickets;
totalRevenue -= refundAmount;
emit TicketRefund(msg.sender, _index, _tickets);
}
function getTicketsLength() public view returns (uint) {
return moviesLength;
}
function getUserTickets(address _user, uint _index) public view returns (uint) {
return userTickets[_user][_index];
}
function getTotalRevenue() public view returns (uint) {
return totalRevenue;
}
}
How The Contract Works
Let’s explain how the contract works!
Contract Structure and Imports
Let’s start by importing the necessary contracts and defining the main structure of our contract.
// SPDX-License-Identifier: MIT
pragma solidity >=0.7.0 <0.9.0;
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
contract Movietickets is Ownable {
// Contract implementation goes here
}
In this code snippet, we import the Ownable contract from the OpenZeppelin library, which provides basic access control functionality. We also import the IERC20 contract, which defines the standard interface for ERC20 tokens. The Movietickets contract inherits from Ownable, making it the contract owner.
Define MovieTicket Structure and Variables
Next, we define the structure of a movie ticket and declare the required variables.
struct Movieticket {
address payable admin;
string name;
string image;
string filmIndustry;
string genre;
string description;
uint price;
uint sold;
uint ticketsAvailable;
bool forSale;
}
uint internal moviesLength = 0;
address internal cUsdTokenAddress = 0x874069Fa1Eb16D44d622F2e0Ca25eeA172369bC1;
mapping (uint => Movieticket) internal movies;
mapping (address => mapping (uint => uint)) internal userTickets;
uint internal totalRevenue = 0;
In this code snippet, we define the Movieticket struct, which represents the attributes of a movie ticket. The struct contains the following fields:
admin: The address of the ticket administrator who manages the ticket sales.name: The name of the movie.image: The image or poster associated with the movie.filmIndustry: The industry to which the movie belongs (e.g., Hollywood, Bollywood).genre: The genre of the movie (e.g., action, comedy).description: A brief description of the movie.price: The price of each ticket in the specified ERC20 token.sold: The number of tickets sold for the movie.ticketsAvailable: The number of tickets currently available for sale.forSale: A flag indicating whether the movie tickets are available for sale.
We also declare several variables:
moviesLength: Stores the number of movies added to the contract.cUsdTokenAddress: The address of the ERC20 token contract used for ticket payments.movies: A mapping that associates each movie index with its corresponding Movieticket struct.userTickets: A mapping that tracks the number of tickets purchased by each user for each movie.totalRevenue: Tracks the total revenue generated from ticket sales.
Define Modifiers
We will define three modifiers to enforce access control and ensure ticket availability.
modifier isTicketAvailable(uint _index, uint _tickets) {
require(movies[_index].ticketsAvailable >= _tickets, "Tickets not sufficient");
_;
}
modifier isTicketForSale(uint _index) {
require(movies[_index].forSale == true, "Ticket is not for sale");
_;
}
modifier isAdmin(uint _index) {
require(msg.sender == movies[_index].admin, "Only admin");
_;
}
-
isTicketAvailable: This modifier ensures that the requested number of tickets is available for purchase. It checks if the ticketsAvailable value for the given movie index is greater than or equal to the requested number of tickets. -
isTicketForSale: This modifier verifies that the movie tickets are currently available for sale. It checks the forSale flag for the given movie index. -
isAdmin: This modifier restricts certain operations to be performed only by the movie administrator. It verifies if the msg.sender (current caller) is the same as the admin address of the movie.
Add Movie
We will implement a function to add movies to the contract.
function addMovie(
string memory _name,
string memory _image,
string memory _filmIndustry,
string memory _genre,
string memory _description,
uint _price,
uint _ticketsAvailable
) public onlyOwner {
uint _sold = 0;
movies[moviesLength] = Movieticket(
payable(msg.sender),
_name,
_image,
_filmIndustry,
_genre,
_description,
_price,
_sold,
_ticketsAvailable,
true
);
moviesLength++;
}
The addMovie function allows the contract owner to add a new movie. It takes the following parameters:
_name: The name of the movie._image: The image or poster associated with the movie._filmIndustry: The industry to which the movie belongs._genre: The genre of the movie._description: A brief description of the movie._price: The price of each ticket in the specified ERC20 token._ticketsAvailable: The initial number of tickets available for sale.
The function creates a new Movieticket struct with the provided details and adds it to the movies mapping using the moviesLength as the index. The moviesLength is then incremented.
Get Movie Ticket Details
We will implement a function to retrieve the details of a movie ticket.
function getMovieTicket(uint _index) public view returns (
address payable,
string memory,
string memory,
string memory,
string memory,
string memory,
uint,
uint,
uint,
bool
) {
Movieticket memory m = movies[_index];
return (
m.admin,
m.name,
m.image,
m.filmIndustry,
m.genre,
m.description,
m.price,
m.sold,
m.ticketsAvailable,
m.forSale
);
}
The getMovieTicket function takes a movie index as input and returns the details of the corresponding movie ticket. It returns a tuple containing the following information:
admin: The address of the ticket administrator.name: The name of the movie.image: The image or poster associated with the movie.filmIndustry: The industry to which the movie belongs.genre: The genre of the movie.description: A brief description of the movie.price: The price of each ticket in the specified ERC20 token.sold: The number of tickets sold for the movie.ticketsAvailable: The number of tickets currently available for sale.forSale: A flag indicating whether the movie tickets are available for sale.
The function retrieves the corresponding Movieticket struct from the movies mapping using the provided index and returns the values as a tuple.
Add Tickets
We will implement a function to add more tickets to a movie.
function addTickets(uint _index, uint _tickets) external isAdmin(_index) {
require(_tickets > 0, "Number of tickets must be greater than zero");
movies[_index].ticketsAvailable += _tickets;
}
The addTickets function allows the movie administrator to add more tickets to a movie. It takes the following parameters:
_index: The index of the movie for which tickets are to be added._tickets: The number of tickets to add.
The function verifies that the number of tickets to add is greater than zero. It then increases the ticketsAvailable value for the specified movie index by the provided number of tickets.
Change Ticket Sale Status
We will implement a function to change the sale status of a movie ticket.
function changeForSale(uint _index) external isAdmin(_index) {
movies[_index].forSale = !movies[_index].forSale;
}
The changeForSale function allows the movie administrator to toggle the sale status of a movie ticket. It takes the movie index as a parameter.
The function flips the value of the forSale flag for the specified movie index. If the ticket was previously for sale, it will be marked as not for sale, and vice versa.
Remove Ticket
We will implement a function to remove a movie ticket from the contract.
function removeTicket(uint _index) external isAdmin(_index) {
movies[_index] = movies[moviesLength - 1];
delete movies[moviesLength - 1];
moviesLength--;
}
The removeTicket function allows the movie administrator to remove a movie ticket from the contract. It takes the movie index as a parameter.
The function replaces the ticket at the specified index with the ticket stored at the end of the movies array. It then deletes the duplicate entry at the end of the array and decrements the moviesLength variable.
Block Tickets
We will implement a function to block a certain number of tickets for a movie.
function blockTickets(uint _index, uint _tickets) external isAdmin(_index) isTicketAvailable(_index, _tickets) {
movies[_index].ticketsAvailable -= _tickets;
}
The blockTickets function allows the movie administrator to block a certain number of tickets for a movie. It takes the following parameters:
_index: The index of the movie for which tickets are to be blocked._tickets: The number of tickets to block.
The function verifies that the requested number of tickets is available for blocking. It then decreases the ticketsAvailable value for the specified movie index by the provided number of tickets.
Buy Movie Tickets
We will implement two functions to allow users to purchase movie tickets.
function buyBulkMovieTicket(uint _index, uint _tickets) external payable isTicketForSale(_index) isTicketAvailable(_index, _tickets) {
require(msg.sender != movies[_index].admin, "Admin cannot buy tickets");
require(
IERC20(cUsdTokenAddress).transferFrom(
msg.sender,
movies[_index].admin,
movies[_index].price * _tickets
),
"Transfer failed."
);
movies[_index].sold += _tickets;
movies[_index].ticketsAvailable -= _tickets;
userTickets[msg.sender][_index] += _tickets;
totalRevenue += movies[_index].price * _tickets;
emit TicketPurchase(msg.sender, _index, _tickets);
}
```solidity
function buyMovieTicket(uint _index) public payable isTicketForSale(_index) isTicketAvailable(_index, 1) {
require(msg.sender != movies[_index].admin, "Admin cannot buy tickets");
require(
IERC20(cUsdTokenAddress).transferFrom(
msg.sender,
movies[_index].admin,
movies[_index].price
),
"Transfer failed."
);
movies[_index].sold += 1;
movies[_index].ticketsAvailable -= 1;
userTickets[msg.sender][_index] += 1;
totalRevenue += movies[_index].price;
emit TicketPurchase(msg.sender, _index, 1);
}
The buyBulkMovieTicket function allows users to purchase multiple movie tickets at once. It takes the following parameters:
_index: The index of the movie for which tickets are to be purchased._tickets: The number of tickets to purchase.
The function verifies that the movie tickets are available for sale and that the requested number of tickets is available. It also ensures that the caller is not the movie administrator.
The function transfers the required amount of ERC20 tokens from the caller to the movie administrator using the transferFrom function of the ERC20 token contract. It then updates the ticket sales and availability data, increments the user’s ticket count for the specified movie, and increases the total revenue of the contract.
Finally, the function emits a TicketPurchase event to notify listeners about the ticket purchase.
The buyMovieTicket function allows users to purchase a single movie ticket. It takes the movie index as a parameter.
The function verifies that the movie ticket is available for sale and that at least one ticket is available. It also ensures that the caller is not the movie administrator.
Similar to the buyBulkMovieTicket function, it transfers the required amount of ERC20 tokens from the caller to the movie administrator using the transferFrom function. It updates the ticket sales and availability data, increments the user’s ticket count, increases the total revenue, and emits a TicketPurchase event.
Refund Tickets
We will implement a function to allow users to refund their purchased tickets.
function refundTickets(uint _index, uint _tickets) external {
require(_tickets > 0, "Number of tickets must be greater than zero");
require(userTickets[msg.sender][_index] >= _tickets, "Insufficient tickets for refund");
uint refundAmount = movies[_index].price * _tickets;
require(
IERC20(cUsdTokenAddress).transferFrom(
movies[_index].admin,
msg.sender,
refundAmount
),
"Transfer failed."
);
movies[_index].sold -= _tickets;
movies[_index].ticketsAvailable += _tickets;
userTickets[msg.sender][_index] -= _tickets;
totalRevenue -= refundAmount;
emit TicketRefund(msg.sender, _index, _tickets);
}
The refundTickets function allows users to refund their purchased tickets. It takes the following parameters:
_index: The index of the movie for which tickets are to be refunded._tickets: The number of tickets to be refunded.
The function verifies that the requested number of tickets to be refunded is greater than zero and that the user has enough tickets to refund for the specified movie.
It calculates the refund amount by multiplying the ticket price with the number of tickets to be refunded.
Using the transferFrom function of the ERC20 token contract, it transfers the refund amount from the movie administrator back to the user.
Then, it updates the ticket sales and availability data, decrements the user’s ticket count, reduces the total revenue of the contract, and emits a TicketRefund event to notify listeners about the ticket refund.
Additional Helper Functions
function getTicketsLength() public view returns (uint) {
return moviesLength;
}
The getTicketsLength function returns the total number of movies in the contract.
function getUserTickets(address _user, uint _index) public view returns (uint) {
return userTickets[_user][_index];
}
The getUserTickets function returns the number of tickets owned by a specific user for a given movie index.
function getTotalRevenue() public view returns (uint) {
return totalRevenue;
}
The getTotalRevenue function returns the total revenue generated by ticket sales in the contract.
You can find the source code here
Deployment
To successfully deploy our smart contract on the Celo network, follow these steps:
- Download the Celo Extension Wallet from the Chrome Web Store. You can find it here here.
- After installing the wallet extension, fund your newly created wallet. You can use the Celo Alfojares faucet, which can be accessed here. This will provide you with Celo testnet tokens for development purposes Here.
- Once the wallet is funded, locate the plugin logo at the bottom left corner of your browser and search for the Celo plugin.
- Install the plugin and you will see the Celo logo appear in the side tab after installation.
- Connect your Celo wallet by clicking on the Celo logo in the side tab.
- Select the contract you wish to deploy.
- Finally, click on the “Deploy” button to initiate the deployment of your smart contract to the Celo network.
By following these steps, you will be able to deploy your smart contract on the Celo network using the Celo Extension Wallet.
Conclusion
Congratulations! You have successfully implemented a Movie Tickets smart contract using Solidity. The contract allows movie administrators to add movies, manage ticket availability, sell tickets to users, refund tickets, and track revenue.
Further learning
I hope you learned a lot from this tutorial. Here are some relevant links that would aid your learning further.
The author
Victor Ubah is a skilled Solidity developer specializing in blockchain technology, particularly in Celo. I have extensive experience in crafting secure and efficient smart contracts for decentralized applications (dApps). With a passion for blockchain development, I strive to create innovative solutions on the Celo platform.
