pragma solidity ^0.4.18; contract LifetimeMembership { bool public win; mapping (address => bool) public members; function becomeMember() external payable { require(msg.value == 1 ether); members[msg.sender] = true; } function winGame() external onlyMember { win = true; // do whatever you want } modifier onlyMember() { require(members[msg.sender] == true); _; } }
0.4.19