Intro

This is my attempt to learn ruby on rails. I will be making sample apps by following tutorials.

Section 1

General commands

rvm list # List down the ruby versions
rvm use [version ] # Switch the ruby version
rails -v # Current rails version

Generate rails project

rails _5.3.4_ new [project_name] # Generate new project 

Run rails project

rails s -p [port] # Run rails by specifying a port
rais s --binding=0.0.0.0 -p [port] # Start with with host name and port

Rails console

rails c # Open the console

Run a ruby file

ruby [filename]

General commands

rails routes # List down all available routes.

Section 2

What is Ruby?

It's a dynamic, OO, Open source programming language developed by Martz. Ruby is considered to follow the principle of POLA (principle of least astonishment). It means that the language behaves in such a way to minimize the confusion for experienced users. It has been for 20+ years. With rails, the popularity of Ruby increased.

Features

• Pure OO Language
• No multiple inheritance
• Modules and Classes
  • Modules contain only methods
  • Supports mixings - Define methods inside modules and use as required them in classes
• Loosely typed
• When a method is called on an object, Ruby only looks up at the name irrespective of the type of object
• Mutating constants wont stop the execution of the program
• Naming:
  • Constants start with capital letter
  • Globals with $
  • Instance var @
  • Class var @@
  • Method names usually follow snake case
• Case sensitive

However, JRuby and Rubinius, which are popular implementations of ruby are compiled

1. Rubinius -COMPILES(Rubinius compiler)-> BYTECODE -COMPILES(Rubinius JIT Compiler (C++)) @ Runtime-> MACHINE CODE rbx compile simple.rb -o simple.bytecode
2. JRuby - -COMPILES(JRuby compiler(Java)-> BYTECODE -COMPILES(Execute bytecode using JVM (JAVA JIT Compiler (C))) @ Runtime-> MACHINE CODE

Usage

rvm jruby-head
ruby simple.rb

Running

jrubyc simple.rb
ls # simple.class simple.rb
javap -c simple.class > simple.bytecode

MORE

Running rails tasks

rails --tasks # view all possible tasks
rails [class_name]:[function_name] # run a task

Section 3

Ruby

1. Ruby Variables local global class instance

2. Strings

• string.class - Type of String

• string.methods - All methods

• .to_s .nil? .empty? .exists? .length .reverse

• ctrl + l will clear up irb

• Strings are pass by value

• #{ } - Acts as a template string for interpolation

• Single quotes doesn't work with interpinolation

• Escape characters also doesn't work with single quotes

• Empty spaces are counted as characters " ".nil? # false

3. Conversions

• .to_s .to_i .to_f .odd? .even? .round

4. Methods and branching

• Return is implicit

5. Comments

• Hash for single line comment
• Multi line comments

=begin
=end

Section 4

Ruby Style Conventions

• Model Name: Singular, First letter upper case.
• Table Name: Plural, lower case model name
• Model File: Snake case
• Controller file: Snake Case
• Classes: Pascal case More @ git

Section 5

Architecture

Rails framework follows the MVC architecture.

The data flow will be as follows

1. Call the route
2. Controller
3. Model Optional
4. Database Optional
5. View

Section 6

Common errors in Ruby are;

NameError: uninitialized constant []
NameError: uninitialized constant Object::Something

• Ruby is case sensitive.

Uninitialized constant

• Extends from NameError exception class
• Thrown when the code refers to an unknown variable (The code can't resolve)
• Classes start with upper case letters, instance variables or class variables start with lower case, Therefore it can be a side effect of misusing.

Section 7

Rails Router has the following types

1. Collection routes (Index action) - Used to show a collection of items /articles
2. Member routes (show action) - Used to show a specific item /articles/:id

You can setup the root route to goto any route.

root articles#index