Learn Rails 5.2: Accelerated Web Development with Ruby on Rails

444 Pages·2018·5.92 MB·English

Learn

Rails 5.2
Accelerated Web Development with
Ruby on Rails
—
Stefan Wintermeyer
Learn Rails 5.2
Accelerated Web Development
with Ruby on Rails
Stefan Wintermeyer
Learn Rails 5.2: Accelerated Web Development with Ruby on Rails
Stefan Wintermeyer
Bochum, Germany
ISBN-13 (pbk): 978-1-4842-3488-4 ISBN-13 (electronic): 978-1-4842-3489-1
https://doi.org/10.1007/978-1-4842-3489-1
Library of Congress Control Number: 2018939414
Copyright © 2018 by Stefan Wintermeyer
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Table of Contents
About the Author ���������������������������������������������������������������������������������������������������xvii
About the Technical Reviewer ��������������������������������������������������������������������������������xix
Preface �������������������������������������������������������������������������������������������������������������������xxi
Introduction ����������������������������������������������������������������������������������������������������������xxiii
Chapter 1: Ruby Introduction ������������������������������������������������������������������������������������1
Ruby 2.5 ........................................................................................................................................1
Basics ...........................................................................................................................................2
Hello World ..............................................................................................................................2
puts and print ..........................................................................................................................2
Comments ...............................................................................................................................3
Help via ri ................................................................................................................................4
irb ............................................................................................................................................4
Ruby Is Object-Oriented ................................................................................................................5
Methods ...................................................................................................................................6
Classes ....................................................................................................................................9
Basic Classes ..............................................................................................................................20
Strings ...................................................................................................................................20
Numbers ................................................................................................................................23
Boolean Values and nil ..........................................................................................................24
Variables .....................................................................................................................................24
Naming Conventions..............................................................................................................25
Scope of Variables .................................................................................................................26
Methods Once Again ...................................................................................................................28
Method Chaining ...................................................................................................................29
Getters and Setters ................................................................................................................29
v
Table of ConTenTs
Converting from One to the Other: Casting ............................................................................33
Method to_s for Your Own Classes ........................................................................................34
Is + a Method? ......................................................................................................................35
if Condition ..................................................................................................................................37
Shorthand ..............................................................................................................................38
else ........................................................................................................................................39
elsif ........................................................................................................................................39
Loops ..........................................................................................................................................39
while and until .......................................................................................................................39
Blocks and Iterators ..............................................................................................................41
Arrays and Hashes ......................................................................................................................44
Arrays ....................................................................................................................................44
Hashes ...................................................................................................................................46
Range ..........................................................................................................................................48
Chapter 2: First Steps with Rails ����������������������������������������������������������������������������51
Environment (Development) ........................................................................................................51
SQLite3 Database ........................................................................................................................52
Why Is It All in English? ...............................................................................................................52
Static Content (HTML and Graphics Files) ...................................................................................52
Create a Rails Project ............................................................................................................52
Static Pages ...........................................................................................................................55
Creating HTML Dynamically with erb ..........................................................................................57
Programming in an erb File ...................................................................................................60
Layouts ..................................................................................................................................64
Passing Instance Variables from a Controller to a View ........................................................66
Partials ..................................................................................................................................67
The Rails Console ........................................................................................................................71
app.........................................................................................................................................73
What Is a Generator? ..................................................................................................................73
Helper..........................................................................................................................................75
vi
Table of ConTenTs
Debugging ...................................................................................................................................76
debug.....................................................................................................................................76
Web Console ..........................................................................................................................76
Other Debugging Tools...........................................................................................................79
Rails Lingo ..................................................................................................................................79
Don’t Repeat Yourself ............................................................................................................79
Refactoring ............................................................................................................................79
Convention Over Configuration ..............................................................................................79
Model View Controller Architecture ............................................................................................80
Model .....................................................................................................................................80
View .......................................................................................................................................80
Controller ...............................................................................................................................80
Abbreviations ..............................................................................................................................81
Chapter 3: ActiveRecord �����������������������������������������������������������������������������������������83
Creating a Database/Model .........................................................................................................83
The Attributes id, created_at, and updated_at ......................................................................86
Getters and Setters ................................................................................................................87
Possible Data Types in ActiveRecord .....................................................................................87
Decimal .................................................................................................................................88
Naming Conventions (Country vs. country vs. countries) ......................................................89
Database Configuration .........................................................................................................89
Adding Records ...........................................................................................................................90
create ....................................................................................................................................90
new ........................................................................................................................................92
new_record? .........................................................................................................................93
first, last, and all .........................................................................................................................94
Populating the Database with seeds.rb ......................................................................................97
It’s All Just Ruby Code ...........................................................................................................98
Generating seeds.rb from Existing Data ................................................................................99
vii
Table of ConTenTs
Searching and Finding with Queries .........................................................................................100
find ......................................................................................................................................101
where ..................................................................................................................................102
order and reverse_order ......................................................................................................108
limit .....................................................................................................................................109
group ...................................................................................................................................110
pluck ....................................................................................................................................110
select ...................................................................................................................................111
first_or_create and first_or_initialize ..................................................................................112
Calculations ..............................................................................................................................112
average ................................................................................................................................112
count....................................................................................................................................113
maximum .............................................................................................................................113
minimum .............................................................................................................................114
sum ......................................................................................................................................114
SQL EXPLAIN .............................................................................................................................114
Batches .....................................................................................................................................115
Editing a Record ........................................................................................................................115
Simple Editing .....................................................................................................................115
Active Model Dirty ...............................................................................................................116
update .................................................................................................................................118
Locking ................................................................................................................................118
has_many, a 1:n Association .....................................................................................................121
Creating Records .................................................................................................................123
Accessing Records ..............................................................................................................126
Searching for Records .........................................................................................................128
delete and destroy ...............................................................................................................130
Options ................................................................................................................................131
Many-to-Many, an n:n Association ............................................................................................133
Preparation ..........................................................................................................................133
The Association ...................................................................................................................134
The Association Works Transparently ..................................................................................135
viii
Table of ConTenTs
Polymorphic Associations .........................................................................................................137
Options ................................................................................................................................142
Deleting/Destroying a Record ...................................................................................................142
destroy .................................................................................................................................143
delete ...................................................................................................................................146
Transactions ..............................................................................................................................147
Scopes ......................................................................................................................................148
Preparation ..........................................................................................................................148
Defining a Scope .................................................................................................................149
Passing In Arguments ..........................................................................................................151
Creating New Records with Scopes ....................................................................................151
Validation ..................................................................................................................................152
Preparation ..........................................................................................................................152
The Basic Idea .....................................................................................................................152
valid? ...................................................................................................................................154
presence ..............................................................................................................................156
length ..................................................................................................................................157
numericality .........................................................................................................................159
uniqueness ..........................................................................................................................161
inclusion ..............................................................................................................................163
exclusion .............................................................................................................................165
format ..................................................................................................................................165
General Validation Options ...................................................................................................166
Writing Custom Validations ..................................................................................................167
Further Documentation ........................................................................................................169
Migrations .................................................................................................................................169
Which Database Is Used? ....................................................................................................173
Creating Index .....................................................................................................................176
Automatically Added Fields (id, created_at, and updated_at) .............................................177
Further Documentation ........................................................................................................178
ix
Table of ConTenTs
Callbacks...................................................................................................................................178
Default Values ...........................................................................................................................180
Chapter 4: Scaffolding and REST ��������������������������������������������������������������������������183
Redirects and Flash Messages .................................................................................................183
Redirects .............................................................................................................................183
redirect_to :back .................................................................................................................186
Flash Messages ...................................................................................................................187
Different Types of Flash Messages ......................................................................................189
Why Are There Flash Messages at All? ................................................................................190
Generating a Scaffold ...............................................................................................................190
The Routes ...........................................................................................................................192
The Controller ......................................................................................................................193
The Views ............................................................................................................................199
When Should You Use Scaffolding? ..........................................................................................211
Example for a Minimal Project ............................................................................................211
Conclusion ...........................................................................................................................216
Chapter 5: Routes �������������������������������������������������������������������������������������������������217
HTTP GET Requests for Singular Resources .............................................................................218
Naming a Route ...................................................................................................................220
as .........................................................................................................................................220
to .........................................................................................................................................220
Parameters ..........................................................................................................................221
Constraints ..........................................................................................................................225
Redirects .............................................................................................................................228
root :to ⇒ welcome#index ........................................................................................................229
resources ..................................................................................................................................229
Selecting Specific Routes with only: or except: ...................................................................230
Nested Resources ................................................................................................................232
Further Information on Routes ..................................................................................................242
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