Ethereum Cookbook

How to do it…

1. Let's consider a lottery system that selects the winning numbers based on a future block hash. While buying a ticket, the user is asked to guess a random set of numbers and is validated against some future block. The prize is given based on how accurate the prediction was.

2. Create a contract by specifying the solidity version and a name:

pragma solidity ^0.4.17;// Decentralized autonomous lotterycontract DAL {    // ...}

3. Create a data structure that will store the bet details of each user. Include the bet amount, guessed number, and a future block number to validate the bet against. Also, create a mapping that maps each bet against a user address:

struct Bet {    // Bet amount    uint256 value;    // Guessed numbers uint32 betHash; ...