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Learn ruby - ruby tutorial - #each graph in ruby on rail swiss knife - ruby examples - ruby programs

names = ['Apple', 'Orange', 'Pine Apple']

for name in names
  puts name
end

You can write:

names = ['Apple', 'Orange', 'Pine Apple']

names.each do |name|
  puts name
end

Or, even more briefly:

names = ['Apple', 'Orange', 'Pine Apple']

names.each { |name| puts name }

names = ['Apple', 'Orange', 'Pine Apple']
uppercase_names = []

names.each do |name|
  uppercase_names << name.upcase end uppercase_names #=> ["APPLE", "ORANGE", "PINE APPLE"]

You can achieve the same thing using #collect as follows:

names = ['Apple', 'Orange', 'Pine Apple']

uppercase_names = names.collect { |name| name.upcase }

uppercase_names #=> ['APPLE', 'ORANGE', 'PINE APPLE']

Learn ruby - ruby tutorial - #select checkbox in ruby on rail swiss knife - ruby examples - ruby programs

cockles_and_mussels = ['alive', 'dead', 'dead', 'alive', 'alive', 'dead']
alive_alive_oh = []

cockles_and_mussels.each do |cockle_or_mussel|
  if cockle_or_mussel == 'alive'
    alive_alive_oh << cockle_or_mussel end end alive_alive_oh #=> ["alive", "alive", "alive"]

Here’s what a solution looks like using #select:

cockles_and_mussels = ['alive', 'dead', 'dead', 'alive', 'alive', 'dead']

alive_alive_oh = cockles_and_mussels.select do |cockle_or_mussel|
  cockle_or_mussel == 'alive'
end

alive_alive_oh #=> ['alive', 'alive', 'alive']

The #reject method is very similar to #select, but the inverse.

cockles_and_mussels = ['alive', 'dead', 'dead', 'alive', 'alive', 'dead']

alive_alive_oh = cockles_and_mussels.reject do |cockle_or_mussel|
  cockle_or_mussel == 'dead'
end

alive_alive_oh #=> ['alive', 'alive', 'alive']

songs = [
  { title: 'Mad World', artist: 'Gary Jules', is_sad: true },
  { title: 'California Gurls', artist: 'Katy Perry', is_sad: false },
  { title: 'Needle in the Hay', artist: 'Elliott Smith', is_sad: true },
  { title: 'Happy', artist: 'Pharrell Williams', is_sad: false }
]

sad_song_to_play_now = songs.detect { |song| song[:is_sad] }

sad_song_to_play_now #=> { title: 'Mad World', artist: 'Gary Jules', is_sad: true }

shopping_cart = [
  { name: 'Vermillion Ink', price: 12.99 },
  { name: 'Azure Ink', price: 9.99 },
  { name: 'LAMY Safari Fountain Pen', price: 49.95 }
]

order_total = shopping_cart.inject(0) do |total, item|
  total + item[:price]
end

order_total #=> 72.93

We can also use #inject to build up data structures. Let’s say we have an array of some employee data:

customer = [['full_name', 'Lois Lane'], ['position', 'Journalist']]

This looks like the kind of data you might extract from a CSV file. It’s in a format we can work with, but we can do better. Let’s use #inject to construct a Hash from this data.

customer = [['full_name', 'Lois Lane'], ['position', 'Journalist']]

customer.inject({}) do |result, element|
  result[element.first] = element.last
  result
end

customer #=> { "full_name"=>"Lois Lane", "position"=>"Journalist" }

pet_names = ['pluto', 'scooby', 'nyan']

find_scooby = pet_names.any? { | pet | pet == 'scooby' }

find_scooby #=> true

ages = [ 19, 59, 70, 23, 140 ]

valid = ages.all? { | age | age > 0 && age <= 122 } valid #=> false

online_opponents = Hash.new
%w(joe87 potatahead coolguy415 ).each_with_index do |item, index|
  online_opponents[item] = index
end

online_opponents   #=> {"joe87"=>0, "potatahead"=>1, "coolguy415"=>2}

superhero_names = ['Wonder Woman', 'Batman', 'Superman']

awesome = superhero_names.include? 'Wonder Woman'

awesome #=> true