Ruby 03 - Iterators and Blocks

01-arrays.rb

# Ranges

range1 = (1..5)
p range1.to_a

range2 = (1...5)
p range2.to_a


# Arrays

musicians = [
  "j dilla",
  "nas",
  "jimi hendrix",
  "beyonce"
]


# Alternative shorthand syntax

# musicians = %w[
#   j\dilla
#   nas
#   jimi\ hendrix
#   beyonce
# ]
p musicians


# CRUD
# Create / Read / Update / Delete


# Create
an_array = []
# an_array = Array.new

p an_array.class


# Read
puts musicians[2]

# Update

# Appending
musicians << "ac/dc"
p musicians

# Prepending
musicians.unshift("nicolai")

# last element
# musicians.last - can only be used for reading
# p musicians[-1]
# p musicians [musicians.length - 1]
musicians[musicians.length - 1] = "jay z"
p musicians

# Inserting
musicians.insert(1, "silverchair")
p musicians

# Delete
# musicians.delete_at(-1) # deleting by index
# p musicians

musicians.delete("beyonce") # deletes all instances/elements
p musicians


# Iterating over the elements of an Array
#.    element in. array
for musician in musicians
  # names = musician.split
  # first_name = names[0].capitalize unless names[0].nil?
  # last_name = names[1].capitalize unless names[1].nil?
  # full_name = "#{first_name} #{last_name}".strip
  puts "Hey, #{musician}!"
end

p musicians


# 1 - Jimi Hendrix

# Iterating over indexes
for index in (0...musicians.size)
  puts "#{index + 1} - #{musicians[index]}"
end

02-iterators.rb

musicians = [
  "j dilla",
  "nas",
  "jimi hendrix",
  "beyonce"
]

# each => returns the original array

# "Hey, jimi hendrix!"
#                element
# array.each { |el| # do somth }

musicians.each do |musician|
  puts "Hey, #{musician}!"
end
p musicians


# each_with_index
musicians.each_with_index do |musician, index|
  puts "#{index + 1} - #{musician}"
end


# upcased_musicians
upcased_musicians = []
musicians.each do |musician|
  upcased_musicians << musician.upcase
end
p musicians
p upcased_musicians

# count musicians that start with j
results = musicians.count do |musician|
  # count the element if condition is true
  musician.start_with?("j")
end

# musicians_with_j = []
musicians_with_j = []
musicians.each do |musician|
  musicians_with_j << musician if musician.start_with?("j")
end
p musicians_with_j

# map => new (transformed) array
result = musicians.map do |musician|
  musician.upcase
end
p musicians
p result

# select => a new array (maybe not of the same length)
# musicians_with_j
musicians_with_j = musicians.select do |musician|
  condition1 = musician.start_with?("j")
  condition2 = musician.length == 7
  condition1 && condition2
  # musician.start_with?("j")
end
p musicians_with_j


# find => element (return the first matched element)
p musicians.find { |musician| musician.start_with?("j") }

# arr.inject(10) { |total, el| total += el }

03-blocks.rb

# Yield

def block_example(string)
  puts "Running the block (line 4)"

  # yield # run the block that is passed into the method call
  yield if block_given? # only run block if it exists

  puts "#{string.upcase} (line 8)"
end


block_example("hello") do
  puts "Hello from inside the block (line 13)"
end


block_example("bye")

def upcase_string(string)
  string.upcase
end

def my_own_each(array)
  for element in array
    yield(element)
  end
end

names = ['john', 'mary']

my_own_each(names) do |name|
  puts upcase_string(name)
end


my_own_each(names) do |name|
  puts name.capitalize
end


my_own_each(names) do |name|
  puts name[0]
end

04-timer.rb

def big_sort
  puts "Running big sort..."
  (0..10000000).sort
end

def small_sort
  puts "Running small sort..."
  (0..100000).sort
end


def timer
  puts "Starting the timer"
  start_time = Time.now

  # big_sort
  # small_sort
  yield

  puts "End the timer"
  end_time = Time.now

  puts end_time - start_time
end

timer do
  big_sort
end

timer do
  small_sort
end