Learn coding with amol

Hello my name is amol sharma or vineet and this is my 11th part of learn coding with amol and in this part we are going to learn Ruby.

 Ruby PART-11

Complete Ruby Programming Guide

A practical Ruby guide (beginner → advanced) with examples and copy buttons — ready for your blog.

1. What is Ruby?

Ruby is a dynamic, open-source programming language focused on simplicity and productivity. It has expressive syntax and powerful built-in libraries. Ruby is widely used for web apps (Rails), scripts, automation, and more.

2. Hello World

# hello.rb

puts "Hello, World!"

3. Run Ruby

• Install Ruby: sudo apt install ruby (Linux), or use rbenv/rvm.
• Run a file: ruby hello.rb
• Start REPL: irb or pry (if installed).

4. Variables & Data Types

# variables.rb

name = "Amol"        # String

age = 21             # Integer

pi = 3.1415          # Float

active = true        # Boolean

arr = [1,2,3]        # Array

h = {name: "Amol"}   # Hash

nil_value = nil      # nil (no value)

5. Operators & Expressions

# ops.rb

a = 10

b = 3

puts a + b    # 13

puts a - b    # 7

puts a * b    # 30

puts a / b    # 3

puts a % b    # 1

# Comparisons

puts a > b     # true

puts a == 10     # true

puts a != b      # true

6. Control Flow

# control.rb

x = 7

if x > 10

  puts "big"

elsif x >= 5

  puts "medium"

else

  puts "small"

end

# case

grade = 'B'

case grade

when 'A' then puts "Excellent"

when 'B' then puts "Good"

else puts "Keep trying"

end

7. Loops & Iteration

# loops.rb

# while

i = 0

while i < 3

  puts i

  i += 1

end

# times

3.times { |n| puts "times: #{n}" }

# for / each

for n in [1,2,3]

  puts n

end

[1,2,3].each do |x|

  puts "each: #{x}"

end

8. Methods (Functions)

# methods.rb

def greet(name)

  "Hello, #{name}!"

end

puts greet("Amol")

# default args

def add(a, b=5)

  a + b

end

puts add(10)   # 15

9. Blocks, Procs & Lambdas

# blocks_procs.rb

# block example

3.times { |i| puts "block: #{i}" }

# proc

p = Proc.new { |x| puts "proc: #{x}" }

p.call(10)

# lambda

l = ->(x) { x * 2 }

puts l.call(4)   # 8

Blocks are anonymous code passed to methods; Procs and lambdas are objects wrapping blocks.

10. Arrays & Hashes

# collections.rb

a = [1,2,3]

a << 4

p a               # [1,2,3,4]

h = {name: "Amol", age: 21}

puts h[:name]     # Amol

# common enumerable methods

a.map { |x| x * 2 }         # [2,4,6,8]

a.select { |x| x.even? }    # [2,4]

a.reduce(0) { |s,x| s + x } # sum

11. Classes & OOP

# person.rb

class Person

  attr_accessor :name, :age

  def initialize(name, age=0)

    @name = name

    @age = age

  end

  def greet

    "Hello, #{@name} (#{@age})"

  end

  def self.species

    "Homo sapiens"

  end

end

p = Person.new("Amol", 21)

puts p.greet

puts Person.species

12. Modules & Mixins

# modules.rb

module Walkable

  def walk

    "Walking..."

  end

end

class Dog

  include Walkable

end

d = Dog.new

puts d.walk   # Walking...

13. Exception Handling

# exceptions.rb

begin

  raise "Oops!"

rescue => e

  puts "Error: #{e.message}"

ensure

  puts "Always runs"

end

14. File I/O

# file_io.rb

File.open("sample.txt", "w") do |f|

  f.puts "Hello from Ruby"

end

txt = File.read("sample.txt")

puts txt

15. Gems & Bundler

• Install gem: gem install sinatra
• Use Bundler: create Gemfile and run bundle install

# Gemfile example

source "https://rubygems.org"

gem "sinatra"

gem "pg"

16. Simple Web App — Sinatra

# app.rb (Sinatra)

require "sinatra"

get "/" do

  "Hello from Sinatra!"

end

# Run: ruby app.rb

# Visit: http://localhost:4567

For larger web apps use Ruby on Rails.

17. Ruby on Rails (quick intro)

• Create app: gem install rails then rails new blog
• MVC framework: Models (ActiveRecord), Views, Controllers
• Database migration: rails db:migrate

Rails is a full-stack framework — if you want, I can make a separate Rails guide with examples.

18. Threads & Concurrency

# threads.rb

threads = []

5.times do |i|

  threads << Thread.new do

    sleep rand(0.1..0.5)

    puts "Thread #{i} done"

  end

end

threads.each(&:join)

Note: Ruby MRI has a GIL — for CPU-bound parallelism explore JRuby or processes.

19. Testing

# simple_test.rb (minitest)

require "minitest/autorun"

class TestMath < Minitest::Test

  def test_add

    assert_equal 4, 2 + 2

  end

end

20. Useful Ruby Standard Library

• net/http — HTTP client
• json — JSON parsing
• fileutils — File operations
• date / time — Date & Time

21. Common CLI Tips

• Run script: ruby script.rb
• Interactive: irb or pry
• Check version: ruby -v
• Format code: use rubocop or rufo

22. Example: Small CRUD in Plain Ruby (Memory)

# crud.rb

class Store

  def initialize

    @items = {}

    @id = 0

  end

  def create(name)

    @id += 1

    @items[@id] = {id: @id, name: name}

  end

  def read(id)

    @items[id]

  end

  def update(id, name)

    @items[id][:name] = name if @items[id]

  end

  def delete(id)

    @items.delete(id)

  end

  def all

    @items.values

  end

end

s = Store.new

s.create("Item A")

s.create("Item B")

p s.all

23. Security Tips

• Always validate user input
• Use parameterized queries for DB access (ActiveRecord / Sequel)
• Sanitize HTML output (e.g., Rails auto-escapes ERB)
• Keep gems updated

24. Learning Path & Resources

1. Begin: learn syntax, methods, arrays & hashes
2. Intermediate: OOP, blocks, enumerables, file I/O
3. Web: Sinatra first, then Rails
4. Advanced: concurrency, native extensions, performance

If you want, I can create a downloadable PDF handbook or a Rails guide to pair with this Ruby guide.

Ready to post — copy the whole HTML and paste into your Blogger post (HTML mode). Want this also as a PDF or a shorter cheat-sheet for readers? Reply and I’ll generate it.

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