Programming Crystal: Create High-Performance, Safe, Concurrent Apps

Cover....1

Table of Contents....7

Preface....11

Who This Book Is For....11

What’s in This Book....11

How to Read This Book....13

Conventions Used in This Book....14

Web Resources and Feedback....15

Downloading Sample Code....15

Acknowledgments....16

Part I—Getting Started....17

1. Diving into Crystal....18

A Programming Language for Humans and Computers....18

Slick As Ruby, But Way Faster....19

Almost As Fast As C....22

Speeding Up the Web....24

Talking to Databases....26

More Safety Through Types....27

No to the Billion-Dollar Mistake....28

Batteries Included....29

Putting Crystal to Good Use....30

A Company’s Story Crystallized: Red Panthers....31

Wrapping Up....33

2. Crystal Foundations....34

Using Basic Variables and Types....34

Variable Operations....37

Structuring Data with Container Types....38

Controlling the Flow....43

Using Methods....48

Organizing Code in Classes and Modules....49

Executing Code Concurrently Through Fibers....53

A Company’s Story Crystallized: Dev Demand....54

Wrapping Up....55

Part II—Building Blocks....56

3. Typing Variables and Controlling the Flow....57

Converting Data Between Types....58

Getting Input....60

Putting It Together—Converting Currencies 1....62

Exception Handling for Faulty Input....64

Chaining Methods....66

Getting Input from Command-Line Arguments....67

Using String Methods....68

Using Symbols as Identifiers....71

Using Enums....72

Using Regular Expressions....72

Putting It Together—Converting Currencies 2....73

Beyond Hashes and Arrays: More Composite Types....74

Nilable Types....76

Controlling the Flow and Types....78

A Company’s Story Crystallized: Linkfeed....81

Wrapping Up....82

4. Organizing Code in Methods and Procs....83

Passing Arguments....84

Returning Values....86

Working with Yield, Procs, and Blocks....88

Overloading and Multiple Dispatch....94

Using a Shorter Syntax for Exception Handling....97

Using Recursive Methods....98

A Company’s Story Crystallized: Duo Design....100

Wrapping Up....102

5. Using Classes and Structs....103

Converting a Ruby Class to Crystal....103

Structuring a Class....110

Applying Inheritance....113

Controlling Visibility....116

Working with Structs....121

Viewing the Type Hierarchy....123

Some Nice Tricks....124

A Company’s Story Crystallized: LI-COR Biosciences....128

Wrapping Up....129

6. Working with Modules....130

Combining Files with Require....130

Using Modules as Namespaces....133

Letting Modules Extend Themselves....135

Mixing in Modules....136

How the Compiler Finds Methods....137

Applying Built-In Modules....138

A Company’s Story Crystallized: Diploid....140

Wrapping Up....142

7. Managing Projects....143

Creating a Shard....143

Formatting Code....146

Documenting a Project....146

Writing Tests with Spec....148

Using External Libraries....152

Benchmarking Your Code....156

Deploying a Crystal App....158

A Company’s Story Crystallized: Diploid—Part 2....158

Wrapping Up....160

Part III—Advanced Crystal....161

8. Advanced Features....162

DRY Your Code with Macros....162

Low-Level Programming and C Bindings....167

Creating Concurrent Code....170

Accessing Databases....178

A Company’s Story Crystallized: NeuraLegion....182

Wrapping Up....183

9. Using Web Frameworks and Shards....184

Build Web Applications with the Kemal and Amber Frameworks....184

A Brief Tour of the Shard Ecosystem....198

A Company’s Story Crystallized: Kemal in Production....200

Wrapping Up and Afterword....201

Part IV—Appendices....202

A1. Setting Up a Crystal Environment....203

Working with Crystal Online....203

Installing Crystal on Your Machine....204

Compiling Code....205

Using Editors and IDEs....207

Working with Crystal Playground....210

Using Crystal Documentation....213

Wrapping Up....214

A2. Porting Ruby Code to Crystal....215

Ruby Extensions in Crystal....217

A3. Your Turn Answers....218

Chapter 2: Crystal Foundations....218

Chapter 3: Typing Variables and Controlling the Flow....219

Chapter 4: Organizing Code in Methods and Procs....220

Chapter 5: Using Classes and Structs....220

Chapter 6: Working with Modules....221

Chapter 7: Managing Projects....221

Chapter 8: Advanced Features....221

Chapter 9: Web Frameworks and the Shard Ecosystem....222

Appendix 1: Setting Up a Crystal Environment....222

Index....223

– SYMBOLS –....223

– A –....223

– B –....224

– C –....224

– D –....226

– E –....226

– F –....227

– G –....227

– H –....227

– I –....228

– J –....228

– K –....228

– L –....228

– M –....229

– N –....230

– O –....230

– P –....230

– Q –....231

– R –....231

– S –....232

– T –....233

– U –....234

– V –....234

– W –....234

– Y –....234

Crystal is for Ruby programmers who want more performance, or for developers who enjoy working in a high-level scripting environment. Crystal combines native execution speed and concurrency with Ruby-like syntax, so you will feel right at home. This book, the first available on Crystal, shows you how to write applications that have the beauty and elegance of a modern language, combined with the power of types and modern concurrency tooling. Now you can write beautiful code that runs faster, scales better, and is a breeze to deploy.

Crystal is elegant to read and easy to program like Ruby, allowing full object-oriented development. Its compiler is powerful enough to nearly always infer the type of your variables. So you get the benefits of a statically typed language: more robust code, safety and execution speed, while still reaching high productivity in development. Null pointer exceptions as in JavaScript, Java or C#, are a thing of the past: Crystal annihilates them, just like Rust.

Explore the building blocks and design of the language, and how you can use the Crystal tool-chain to build and manage powerful applications. Harness the power of the macro system, as well as how to work with fibers and channels, making concurrency as easy as possible. Learn how to use the Kemal web framework and access databases, and how to tap the potential of existing Crystal libraries. Find the spot that Crystal fills in today's software world with real-world examples.

With Crystal, you can combine the best of both worlds: the high-level coding of dynamic languages, and the safety and blazing performance of a natively compiled language.

What You Need:

To develop in Crystal, you only need Crystal v 0.26 the latest version, a common text editor and a browser.