Since Filip told us to start programming on our own, after the end of the smart contract programming 101 course, I decided to work on my own little project.
I would love to hear what you guys did as a project and try to read your code. It took me 3 hours to build mine (is this fast/slow for the task I assigned to myself?), some parts were really frustrating, because we didn’t learn things that i needed in the course, but here it is:
I am a huge classical music fan and one of my favorite pianist is Evgeny Kissin. I created a smart contract about selling tickets, it is structured like this:
- Only 100 tickets available
- Price for one ticket is 0.36 Ether
- Customer pays by registering with name and age
- Refund is possible (allow owner to use a button to delete customer of the list, if for example the customer contacted, and the price gets transacted back to the customer)
- Customers under the age of 25 get a discount for 0.14 Ether
- There is a button for “tickets left”, so people know if it is sold out or not
- Only the owner can get the information (like the name) of the customers listed
- Owner can withdraw the money from the tickets
- Contract can be destroyed (usefull for example if it only sells 95 tickets, and people cannot buy a ticket on accident if they didn’t realize the concert is already over)
I should’ve added comments to the contract, but to be honest I am too lazy for that now, sorry 
Also, let me know if you find any bugs or can give any tips.
Evgeny.sol
import "./Ownable.sol";
import "./Destroyable.sol";
pragma solidity 0.5.12;
contract Evgeny is Ownable, Destroyable{
struct Customer{
address payable money;
uint id;
string lastName;
string surName;
uint age;
bool young;
}
uint private balance;
Customer [] private contacters;
function createCustomer(string memory lastName, string memory surName, uint age) public payable{
require(contacters.length<100);
balance += msg.value;
Customer memory newCustomer;
newCustomer.lastName = lastName;
newCustomer.surName = surName;
newCustomer.age = age;
if(age <= 25){
newCustomer.young = true;
require(msg.value >= 140000000000000000 wei);
}
else {
newCustomer.young = false;
require(msg.value >= 360000000000000000 wei);
}
newCustomer.money = msg.sender;
contacters.push(newCustomer);
}
function getCustomer(uint index) public view onlyOwner returns(string memory lastName, string memory surName, uint age, address money){
return (contacters[index].lastName, contacters[index].surName, contacters[index].age, contacters[index].money);
}
function withdrawAll() public onlyOwner{
uint toTransfer = balance;
balance = 0;
msg.sender.transfer(toTransfer);
}
function ticketsLeft() public view returns(uint count) {
count = 100 - contacters.length;
return count;
}
function deleteCustomer (uint index) public onlyOwner {
if (contacters[index].age <= 25){
balance = balance - 140000000000000000 wei;
contacters[index].money.transfer(140000000000000000 wei);
}
else {
balance = balance - 360000000000000000 wei;
contacters[index].money.transfer(360000000000000000 wei);
}
delete contacters[index];
}
}
Ownable.sol
pragma solidity 0.5.12;
contract Ownable {
address internal owner;
modifier onlyOwner(){
require(msg.sender == owner);
_;
}
constructor() public {
owner = msg.sender;
}
}
Destroyable.sol
import "./Ownable.sol";
pragma solidity 0.5.12;
contract Destroyable is Ownable {
function endContract() public onlyOwner {
selfdestruct(msg.sender);
}
}
