Book Image

Building Blockchain Projects

By : Narayan Prusty
Book Image

Building Blockchain Projects

By: Narayan Prusty

Overview of this book

Blockchain is a decentralized ledger that maintains a continuously growing list of data records that are secured from tampering and revision. Every user is allowed to connect to the network, send new transactions to it, verify transactions, and create new blocks, making it permission-less. This book will teach you what blockchain is, how it maintains data integrity, and how to create real-world blockchain projects using Ethereum. With interesting real-world projects, you will learn how to write smart contracts which run exactly as programmed without any chance of fraud, censorship, or third-party interference, and build end-to-e applications for blockchain. You will learn about concepts such as cryptography in cryptocurrencies, ether security, mining, smart contracts, solidity, and more. You will also learn about web sockets, various API services for Ethereum, and much more. The blockchain is the main technical innovation of bitcoin, where it serves as the public ledger for bitcoin transactions.
Table of Contents (16 chapters)
Title Page
About the Author
About the Reviewers
Customer Feedback

Chapter 7. Building a Betting App

Sometimes, it is necessary for smart contracts to access data from other dapps or from the World Wide Web. But it's really complicated to let smart contracts access outside data due to technical and consensus challenges. Therefore, currently, Ethereum smart contracts don't have native support to access outside data. But there are third-party solutions for Ethereum smart contracts to access data from some popular dapps and from the World Wide Web. In this chapter, we will learn how to use Oraclize to make HTTP requests from Ethereum smart contracts to access data from the World Wide Web. We will also learn how to access files stored in IPFS, use the strings library to work with strings, and so on. We will learn all this by building a football-betting smart contract and a client for it.

In this chapter, we'll cover the following topics:

  • How does Oraclize work?
  • What are Oraclize's various data sources and how do each of them work?
  • How does consensus work in Oraclize...