Chapter 28. 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...
