Week 04 Ruby Part 2 - Code-the-Dream-School/rails-guidebook GitHub Wiki

Week Topic Learning Objectives Key Resources
4 Ruby Part 2
  • Understand blocks in Ruby
  • Ruby functions
  • Classes, instances of a class, instance variables
  • Getters and setters
  • Ruby modules and the require statement
  • Understand the Ruby standard library
  • Understand gems
 Lesson Materials

Coding Assignment

Overview

Lesson 4 Overview

Ruby Blocks

  • Introduction to Blocks: Blocks in Ruby are similar to callbacks in JavaScript, with specific syntax (do...end or {...}) and block arguments.
  • Numbered Block Arguments: Use _1, _2, etc., to refer to block arguments.
  • Methods with Blocks: Methods like each, map, and reduce can take blocks.

Ruby Methods

  • Method Declaration: Use def to declare methods. The last expression's value is returned.
  • Guard Clauses: Use return for early exits.
  • Variable Scope: Variables inside methods are not accessible outside.

Ruby Classes

  • Class Basics: Classes are declared with class and have instance variables and initializer methods.
  • Creating Instances: Use new to create instances.
  • Instance Methods and Accessors: Use attr_accessor for getters and setters or define them explicitly.
  • Class Methods and Variables: Use self for class methods and @@ for class variables.
  • Inheritance: Classes can inherit from other classes.

Ruby Modules

  • Introduction to Modules: Modules are used for code reuse and can be included in classes.

Ruby Require

  • Requiring Files: Use require to include other Ruby files, enabling code organization.

Ruby Standard Library and Ruby Gems

  • Standard Library: Utilize Ruby's standard library, documented at ruby-doc.org.
  • Ruby Gems: Install and use gems from RubyGems.org for reusable libraries.

Assignment Rubric

#1. divisible.rb
def divisible
  (1..100).select { |n| n % 2 == 0 || n % 3 == 0 || n % 5 == 0 }
end

puts divisible

#2. hangman.rb
def hangman(word, letters)
  word.chars.map { |char| letters.include?(char) ? char : '_' }.join
end

puts hangman("bob", ["b"])         # => "b_b"
puts hangman("alphabet", ["a", "h"]) # => "a__ha___"

#3. hash_to_array.rb
def hash_to_array(hash)
  keys = hash.keys
  values = hash.values
  [keys, values]
end

#Collecting user input
hash = {}
5.times do
  print "Enter a key: "
  key = gets.chomp
  print "Enter a value: "
  value = gets.chomp
  hash[key] = value
end

keys, values = hash_to_array(hash)
puts "Keys: #{keys}"
puts "Values: #{values}"

#4. sums.rb
class Sum1
  attr_accessor :total

  def initialize(a, b)
    @total = a + b
  end
end

class Sum2
  def initialize(a, b)
    @a = a
    @b = b
  end

  def new_total
    @a + @b
  end
end

sum1 = Sum1.new(5, 6)
sum2 = Sum2.new(5, 6)

puts sum1.total        # => 11
puts sum2.new_total    # => 11

#5. sort_blocks.rb
class Book
  attr_reader :author, :title, :count

  def initialize(author, title, count)
    @author = author
    @title = title
    @count = count
  end

  def to_s
    "author: #{author} | title: #{title} | count: #{count}"
  end
end

book_array = [
  Book.new("Beatrice Potter", "Peter Rabbit", 25),
  Book.new("Henry Fielding", "Tom Jones", 12),
  Book.new("Bob Woodward", "All the President's Men", 30)
]

#Sorting by author
sorted_by_author = book_array.sort { |a, b| a.author.downcase <=> b.author.downcase }
puts "Sorting alphabetically by author"
puts sorted_by_author

#Sorting by title
sorted_by_title = book_array.sort { |a, b| a.title.downcase <=> b.title.downcase }
puts "Sorting alphabetically by title"
puts sorted_by_title

#Sorting by count
sorted_by_count = book_array.sort { |a, b| a.count <=> b.count }
puts "Sorting by number of copies"
puts sorted_by_count

#6. block_method.rb
def do_calc
  yield(7, 9)
end

puts do_calc { |a, b| a + b }    # => 16
puts do_calc { |a, b| a * b }    # => 63

#7. chuck_norris_facts.rb
require 'faker'

loop do
  print "Do you want to know a fact about Chuck Norris? (yes/no): "
  answer = gets.chomp.downcase
  break if answer != 'yes'

  puts Faker::ChuckNorris.fact
end
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