The Ruby Workshop
A Practical, No-Nonsense Introduction to Ruby Development
Akshat Paul
Peter Philips
Dániel Szabó
Cheyne Wallace
The Ruby Workshop
Copyright © 2019 Packt Publishing
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Authors: Akshat Paul, Peter Philips, Dániel Szabó, and Cheyne Wallace
Technical Reviewers: Jonathan Evans, Jagdish Narayandasani, and Dixitkumar N. Patel
Managing Editor: Snehal Tambe
Acquisitions Editor: Alicia Wooding
Production Editor: Samita Warang
Editorial Board: Shubhopriya Banerjee, Bharat Botle, Ewan Buckingham, Megan Carlisle, Mahesh Dhyani, Manasa Kumar, Alex Mazonowicz, Bridget Neale, Dominic Pereira, Shiny Poojary, Abhishek Rane, Erol Staveley, Ankita Thakur, Nitesh Thakur, and Jonathan Wray
First Published: October 2019
Production Reference: 1301019
ISBN: 978-1-83864-236-5
Published by Packt Publishing Ltd.
Livery Place, 35 Livery Street
Birmingham B3 2PB, UK
Table of Contents
Preface i
1. Writing and Running Ruby Programs 1
Introduction 2
Key Features of Ruby 2
Object-Oriented 3
Interpreted Language 3
Duck Typing and Dynamic Typing 4
Multi-paradigm Language 4
Reflection 5
Metaprogramming 5
Interactive Ruby Shell (IRB) 6
Exercise 1.01: Creating and Assigning Variables 7
Exercise 1.02: Assigning a Variable of One Data Type to a Different Type 8
Exercise 1.03: Getting the Type of a Variable 9
Getting the Details of the Public Methods of an Object 10
Running Ruby Code from Ruby Files 10
Exercise 1.04: Getting User Input in a Ruby Program 11
Standard Data Types 12
Number 12
Exercise 1.05: Performing Common Integer Operations 14
Exercise 1.06: Using Common Integer Methods to Perform Complex Arithmetic 15
Floating-Point Numbers 17
Exercise 1.07: Performing Common Operations for Floating-Point Numbers 17
String 19
Exercise 1.08: Using Common String Methods 21
Exercise 1.09: Performing String Concatenation 24
Exercise 1.10: Performing String Interpolation 26
Exercise 1.11: Extracting and Searching a Substring from a String 26
Exercise 1.12: Replacing Part of a String with Another String 27
Exercise 1.13: Replacing All the Values inside a String Using gsub 28
Exercise 1.14: Splitting a String and Joining a String 29
Activity 1.01: Generating Email Addresses Using Ruby 30
Boolean 31
Activity 1.02: Calculating the Area and Perimeter of a Candy Manufacturing Plant 32
Summary 32
2. Ruby Data Types and Operations 35
Introduction 36
Arrays 36
Iterating Through an Array 38
Operations on Arrays 42
Merging Two Arrays 42
Removing Occurrences of Similar Elements from an Array 42
Inserting Elements into an Array at the End 43
Finding the Last Element of an Array without Modifying It 43
Finding the Last Element of an Array and Removing it 44
Exercise 2.01: Performing Simple Operations on Arrays 44
Creating an Array That Cannot Be Modified 47
Finding All the Unique Elements in an Array 47
Sorting the Elements of an Array 48
Finding the Number of Elements in an Array 49
Establishing Whether an Element Exists in an Array (Case-Sensitive) 49
Converting Elements of an Array into a String 50
Exercise 2.02: Performing Complex Operations on Arrays 51
Hashes 53
Operations on Hashes 58
Getting Values from the Hash 59
Sorting a Hash 59
Merging Hashes 60
Retrieving Keys or Values from a Hash 61
Deleting a Value from a Hash by Key 61
Removing or Rejecting Elements from a Hash 62
Establishing whether a Hash Contains a Particular Value 62
Exercise 2.03: Converting a Time String to a Hash 63
Ruby Methods 64
Passing Arguments to a Method 65
Ruby Methods with Default Values 65
Return Value(s) from Methods 69
Naming Conventions for Methods 71
Activity 2.01: Dice Roller Program 72
Summary 73
3. Program Flow 75
Introduction 76
Boolean Operators 76
The AND Operator 77
The OR Operator 78
The NOT Operator 79
Truth Tables 79
Truthiness 81
Precedence 84
Exercise 3.01: Implementing Boolean Operators 86
Conditional Expressions 87
The if Statement 87
The else Statement 88
The elsif Statement 88
The unless Statement 89
Comparison 90
Comparison Operators 90
Comparing Strings 92
Exercise 3.02: Creating a Method to Check Your Balance 93
The case/when Statement 94
The === Operator 96
The Ternary Operator 97
Exercise 3.03: Speed Determiner 98
Loops 103
The while/do Loop 103
Exercise 3.04: Developing a Mind Reader 104
The until/do Loop 108
The do/while Loop 108
Iterators and Enumerators 110
The each Method 110
The each_with_index Method 112
The map/collect Loop 114
Exercise 3.05: Developing an Arbitrary Math Method 117
Activity 3.01: Number-Guessing Game 119
Summary 121
4. Ruby Methods 123
Introduction 124
The Basic Structure of the Ruby Method 125
Method Components: Signature and Implementation 126
The Method Signature 126
Method Arguments 128
Positional Arguments 128
Variable Scope 129
Optional Parentheses and Code Style 131
Mandatory and Optional Arguments 132
Keyword Arguments 133
Return Values 134
Multiple Return Values 134
Exercise 4.01: Performing Operations on an Array 137
The Splat Operator 139
The Single Splat (*) Operator 139
The Double Splat (**) Operator 140
Exercise 4.02: Creating a Method to Take Any Number of Parameters 141
Duck Typing 143
Sending a Message 144
Using Built-In Modules: Time and Math 146
Math 146
Exercise 4.03: Using the Math Library to Perform Mathematical Operations 146
Time 150
Exercise 4.04: Performing Method Operations with the Time Module 151
Activity 4.01: Blackjack Card Game 154
Summary 156
5. Object-Oriented programming with Ruby 159
Introduction 160
Classes and Objects 161
Instance Methods 162
Getters and Setters 164
Exercise 5.01: Modeling a Company's Organizational Chart Using Classes 167
Class Methods 174
Method 1: Calling a Method Directly on the Class 175
Method 2: Using the self Keyword 175
Class Variables 176
Exercise 5.02: Generating URLs for Sharing Content on Social Platforms 179
Inheritance 183
The Inheritance of Methods 184
The Inheritance of Variables 187
Calling super 188
The Different Ways to Call super 190
Calling super without Arguments 191
Calling super with Arguments 191
Calling super with the Naked Splat Operator 191
Exercise 5.03: Modelling a Class for Location Addresses 195
Encapsulation 198
Public Methods 198
Private Methods 199
Protected Methods 200
Exercise 5.04: Demonstrate the Visibility Rules of Ruby Methods 201
Bypassing Visibility 207
A Quick Note about File Organization 209
Activity 5.01: Voting Application for Employee of the Month 209
Summary 211
6. Modules and Mixins 213
Introduction 214
Including Modules 214
Exercise 6.01: Controlling the Operations of Services in an Application 217
Inheritance with Module Methods 218
Inclusion Ordering 220
extend 221
Exercise 6.02: Extending Your Modules with Class and Instance Methods 223
Module Callbacks 226
Exercise 6.03: Using Module Functions to Extend Classes 227
Importing Modules as Class Methods using Extended 229
Combining include and extend 229
Enumerated Types 231
Exercise 6.04: Writing a Module to Define Payment Methods for a Product Application 232
Module Methods 237
Namespaces 238
Exercise 6.05: How to Reuse Constants with a Namespace 240
prepend 242
prepend with Subclasses 244
Exercise 6.06: Prepending Modules to Classes 248
Activity 6.01: Implementing Categories on the Voting Application Program 249
Summary 250
7. Introduction to Ruby Gems 253
Introduction 254
RubyGems and the require Method 254
gem search 256
gem install 257
gem dependency 257
gem Versioning 258
gem list 259
Using Gems in Your Code 260
Exercise 7.01: Installing and Using a Ruby Gem 261
File I/O 262
Creating Files 262
Reading Files 263
Using the File.read Method 264
Using the File.open Method 264
Using the File.foreach Method 264
read versus open versus foreach 265
Writing to Files 265
Using the File.new Method (Initializer) 266
Using the File.open Method with a Block Method 266
Using the File.write Method 266
File.open versus File.new 267
File Modes 267
File Helpers 268
Handling CSV Data 269
Reading Data from a CSV File Using CSV.read 270
Using Column Headers as Field Names 272
Exercise 7.02: Reading Data from a .csv File and Printing a Few Columns 274
Reading Data from a .csv File Using CSV.foreach 275
Response Type Variations 276
Writing Data 277
Writing CSV Data from an Enumerable 278
Exercise 7.03: Writing an Array of Users to a CSV File 279
Service Objects 280
The Single Responsibility Principle 281
Service Objects versus Modules 282
Class Method Execution 286
Exercise 7.04: Building a Service Object 287
Activity 7.01: Presenting Voting Data in CSV Format Using Ruby Gems 288
Summary 290
8. Debugging with Ruby 293
Introduction 294
Logging and Debugging 294
Logging with the logger Class 295
Basic Logging 296
Log Levels 297
Exercise 8.01: Logging User Information 301
Exercise 8.02: Creating a Basic Exception Logger 303
Setting Log Levels by String 304
Log Output 305
STDOUT 305
STDERR 306
File 306
Log Formatting 307
Custom Date Formats 307
Custom String Formats 309
Time Zones and UTC 310
Log File Management 311
Size-Based Retention 311
Time-Based Retention 313
Exercise 8.03: Creating a Rolling Log File 314
Debugging 315
Debugging Concepts 315
Breakpoints 315
Stack Trace/Call Stack/Back Trace 317
Viewing the Stack Trace 319
StepOver, StepInto, and StepOut 319
Debugging via the CLI with byebug 321
Conditional Debugging 324
Navigating with byebug 325
Exercise 8.04: Debugging with byebug 327
Debugging with Visual Studio Code 328
Setting Breakpoints 332
Logpoints 334
The Debug Console 334
Exercise 8.05: Debugging with Visual Studio Code 336
Activity 8.01: Perform Debugging on a Voting Application 340
Summary 341
9. Ruby Beyond the Basics l 345
Introduction 346
Metaprogramming 346
Blocks 347
Syntax for Blocks 347
With do/end 347
With curly brackets ({}) 348
yield with Blocks 350
Exercise 9.01: Building a Simple Calculator 352
block_given? with Blocks 353
Exercise 9.02: Building a Flight Status Display System 354
The proc Object 356
Exercise 9.03: Performing the sum Function on a Range of Numbers 357
Exercise 9.04: Calculating Profit Using proc on an Input Price List 358
Lambdas 359
Exercise 9.05: Creating a Program to Sum a Range of Numbers Using Lambdas 359
proc versus lambda 360
The Story of the Chef and the Restaurant 361
Activity 9.01: Invoice Generator 363
Summary 364
10. Ruby Beyond the Basics ll 367
Introduction 368
Metaprogramming – A Deep Dive 368
Opening Classes 368
Exercise 10.01: Opening the Ruby String Class to Add a New Method to it 369
Monkey Patching 370
Exercise 10.02: Using Monkey Patching to Add/Subtract Values 372
method_missing 373
Exercise 10.03: Managing Ghost Methods for the Company Class 377
The Define Method 379
Exercise 10.04: Creating a Welcome Message Program Using define_method 380
HTTP Requests 381
HTTP Requests with Ruby 382
Exercise 10.05: Creating a Ruby Program to Make a Successful GET Request 382
Status Codes 383
Exercise 10.06: Creating a POST Request Using Ruby 384
Creating a Ruby Gem 386
Exercise 10.07: Creating Your Own Ruby Gem 386
Activity 10.01: Implementing GET and POST Data to an External Server 389
Summary 390
11. Introduction to Ruby on Rails l 393
Introduction 394
MVC 394
Model 395
View 395
Controller 395
Generating Our First Rails App 396
Exercise 11.01: Generating a Simple Rails Application 397
Anatomy of a Rails application 400
Exercise 11.02: Replacing the Default Page 403
Exercise 11.03: Displaying a Page Heading from the Value Served from Its Action 405
Extending Our View and Controller 406
Exercise 11.04: Adding a Resource to the Rails Application 407
Models, Migrations, and Databases 412
Exercise 11.05: Creating a Review Model for citireview 414
The Rails Console 418
Exercise 11.06: Completing the Reviews Web Application 421
The devise Ruby Gem 425
Activity 11.01: Adding Authentication for the Review Application 425
Summary 427
12. Introduction to Ruby on Rails ll 429
Introduction 430
Associations 430
belongs_to 431
has_one 432
has_many 432
has_many :through 433
has_one :through 434
has_and_belongs_to_many 435
Exercise 12.01: Creating a Model to Enable Users to Comment on Reviews on the CitiReview Application 436
Validations 443
Database Validations 443
Controller-Level Validations 443
Client-Side Validations 444
Model-Level Validations 444
Methods that Trigger Validations 444
Methods that Skip Validations 444
Checking Validations 445
Exercise 12.02: Adding Validation for the Citireview Application 445
Scaffolding 448
Exercise 12.03: Using Rails Scaffolding to Create a Rails Application for a Store with a List of Products 448
Activity 12.01: Create a Blog Application and Host It Live on a Cloud Platform 452
Summary 454
Appendix 457
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