Book Image

Blockchain Development with Hyperledger

By : Salman A. Baset, Luc Desrosiers, Nitin Gaur, Petr Novotny, Anthony O'Dowd, Venkatraman Ramakrishna, Weimin Sun, Xun (Brian) Wu
Book Image

Blockchain Development with Hyperledger

By: Salman A. Baset, Luc Desrosiers, Nitin Gaur, Petr Novotny, Anthony O'Dowd, Venkatraman Ramakrishna, Weimin Sun, Xun (Brian) Wu

Overview of this book

Blockchain and Hyperledger are open source technologies that power the development of decentralized applications. This Learning Path is your helpful reference for exploring and building blockchain networks using Ethereum, Hyperledger Fabric, and Hyperledger Composer. Blockchain Development with Hyperledger will start off by giving you an overview of blockchain and demonstrating how you can set up an Ethereum development environment for developing, packaging, building, and testing campaign-decentralized applications. You'll then explore the de facto language Solidity, which you can use to develop decentralized applications in Ethereum. Following this, you'll be able to configure Hyperledger Fabric and use it to build private blockchain networks and applications that connect to them. Toward the later chapters, you'll learn how to design and launch a network, and even implement smart contracts in chain code. By the end of this Learning Path, you'll be able to build and deploy your own decentralized applications by addressing the key pain points encountered in the blockchain life cycle. This Learning Path includes content from the following Packt products: • Blockchain Quick Start Guide by Xun (Brian) Wu and Weimin Sun • Hands-On Blockchain with Hyperledger by Nitin Gaur et al.
Table of Contents (25 chapters)
Title Page
Copyright
About Packt
Contributors
Preface
Index

Chaincode design topics


Composite keys

We often need to store multiple instances of one type on the ledger, such as multiple trade agreements, letters of credit, and so on. In this case, the keys of those instances will be typically constructed from a combination of attributes—for example, "Trade" + ID, yielding ["Trade1","Trade2", ...]. The key of an instance can be customized in the code, or API functions can be provided in SHIM to construct a composite key (in other words, a unique key) of an instance based on a combination of several attributes. These functions simplify composite key construction. Composite keys can then be used just as a normal string key is used to record and retrieve values using the PutState() and GetState() functions.

The following snippet shows a list of functions that create and work with composite keys:

// The function creates a key by combining the attributes into a single string. 
// The arguments must be valid utf8 strings and must not contain U+0000 (nil byte...