ciga-dapp/contracts/ShowFactory.sol

pragma solidity ^0.4.23;

import "./Ownable.sol";

contract ShowFactory is Ownable {
    event NewShow(uint id, string name, bytes music);

    struct Show {
        string name;
        bytes dance;
        bytes music;
    }

    Show[] public shows;

    mapping (uint=>address) public showToOwner;
    mapping (address=>uint) public ownerShowCount;

    modifier onlyOwnerOf(uint id) {
        require(msg.sender == showToOwner[id]);
        _;
    }

    function _createShow(string name, bytes dance, bytes music) internal {
        uint id = shows.push(Show(name, dance, music)) - 1;
        showToOwner[id] = msg.sender;
        ownerShowCount[msg.sender]++;
        emit NewShow(id, name, music);
    }

    function createFirstShow(string name, bytes dance, bytes music) public {
        require(ownerShowCount[msg.sender] == 0); // The 1st show is free
        _createShow(name, dance, music);
    }
}