Professional Clojure

INTRODUCTION xv CHAPTER 1: HAVE A BEGINNER’S MIND 1 Functional Thinking 2 Value Oriented 2 Thinking Recursively 5 Higher Order Functions 8 Embracing Laziness 11 When You Really Do Need to Mutate 12 Nil Punning 15 The Functional Web 16 Doing Object-Oriented Better 16 Polymorphic Dispatch with defmulti 18 Defining Types with deftype and defrecord 20 Protocols 21 Reify 22 Persistent Data Structures 23 Shaping the Language 27 Summary 29 CHAPTER 2: RAPID FEEDBACK CYCLES WITH CLOJURE 31 REPL-Driven Development 32 Basic REPL Usage with Leiningen 32 Remote REPLs with nREPL 34 REPL Usage with a Real Application 35 Connecting Your Editor to a REPL 39 Reloading Code 40 Reloading Code from the REPL 40 Automatically Reloading Code 43 Writing Reloadable Code 49 Summary 51 CHAPTER 3: WEB SERVICES 53 Project Overview 53 Namespace Layout 54 Elements of a Web Service 55 Libraries, Not Frameworks 55 HTTP 55 Routing 64 JSON Endpoints 70 Example Service 74 Create the Project 75 Additional Namespaces 75 Default Middleware 77 The Storage Protocol 78 Handlers 83 Middleware 88 Routes 89 Deployment 94 Using Leiningen 94 Compiling an Uberjar or Uberwar 95 Hosting 96 Summary 97 CHAPTER 4: TESTING 99 Testing Basics with clojure.test 100 with-test 101 deftest 101 are 102 Using Fixtures 103 Testing Strategies 104 Tests Against DB 104 Testing Ring Handlers 106 Mocking/Stubbing Using with-redefs 108 Redefining Dynamic Vars 110 Record/Replay with VCR 111 Measuring Code Quality 112 Code Coverage with Cloverage 112 Static Analysis with kibit and bikeshed 114 Keeping Dependencies Under Control 116 Testing Framework Alternatives 119 Expectations 119 Speclj 119 Cucumber 120 Kerodon 126 Summary 127 CHAPTER 5: REACTIVE WEB PAGES IN CLOJURESCRIPT 129 ClojureScript Is a Big Deal 129 A First Brush with ClojureScript 131 Starting a New ClojureScript Project 132 Getting Fast Feedback with Figwheel 132 Creating Components 134 Modeling the Data 135 Responding to Events and Handling State Change 136 Understanding Errors and Warnings 137 Namespace Layout 141 Styling 141 Form Inputs and Form Handling 142 Navigation and Routes 145 HTTP Calls: Talking to a Server 147 Drag and Drop 149 Publishing 150 Reagent in Depth 151 Form 1: A Function That Returns a Vector 151 Form 2: A Function That Returns a Component 152 Form 3: A Function That Returns a Class 153 Sequences and Keys 154 Custom Markup 155 Reactions 156 A Note on Style 158 Testing Components with Devcards 159 Interop with JavaScript 162 One Language, One Idiom, Many Platforms 164 Things to Know About the Closure Compiler and Library 164 Modeling State with DataScript 165 Go Routines in Your Browser with core.async 166 Summary 167 CHAPTER 6: THE DATOMIC DATABASE 169 Datomic Basics 170 Why Datomic? 170 The Datomic Data Model 172 Querying 175 Transactions 181 Indexes Really Tie Your Data Together 183 Datomic’s Unique Architecture 187 Modeling Application Data 188 Example Schema for Task Tracker App 188 Entity ids and Partitions 196 Datomic’s Clojure API 197 Basic Setup 197 Experimenting in the REPL 200 Building Applications with Datomic 206 User Functions 206 Account Functions 209 Task Functions 210 Deployment 213 The Limitations 214 Summary 215 CHAPTER 7: PERFORMANCE 217 What Is Performance? 219 Choosing the Right Data Structure Is a Prerequisite for Performance 219 Benchmarking 221 Timing Slow Things 221 Use Criterium for Timing Fast Things 223 Use Test Selectors for Performance Tests 225 Parallelism 225 Memoization 226 Inlining 227 Persistent Data Structures 228 Safe Mutation with Transients 228 Profi ling 229 Avoiding Reflection with Type Hinting 230 Java Flags 232 Math 232 Summary 232 INDEX 235