• Array
• Enumerator
• Hash
• Files and Directories
• csv
• Goodies
  • Benchmark
• Random

# reject elements. Returns the array without the rejected elements.
  ["", "1", "2"].reject(&:empty?)

# Select elements. Returns an array.
  [10, 2, 1].select { |value| value >= 1 }

# Check elements against a condition. Returns a boolean.
  [132, 12, 0.5].any? { |value| value > 1 }

# Select a random element
  %w(one two three).sample

# Sort hashes
  [{ age: 12, name: "John" }, { age: 21, name: "Betty" }].sort_by { |value_hash| value_hash[:age] }
  
# Count the number of occurences
  %w(one two three one one).count("one") # > 3

# Split in smaller arrays. Returns an enumerator
%w(one two three four five six).each_slice(2)
# > [["one", "two"], ["three", "four"], ["five", "six"]] 

# Make an array out of something.
Array.wrap(something)

(1..4).each_with_object([]) { |item, ob| ob << item * 10 }
=> [10, 20, 30, 40]

> (1..4).each_with_object({}) { |i, ob| ob[i] = i * 10 }
=> {1=>10, 2=>20, 3=>30, 4=>40}

Get all keys recursively in a Hash

def get_all_keys(ha)
  ha.each_with_object([]) do |(key, value), keys|
    keys << key
    keys.concat(get_all_keys(value)) if value.is_a? Hash
  end
end

Directories

Dir.pwd                             # Current directory
Dir.chdir "take_me_home/directory/" # Change directory
Dir.glob("*")                       # Array of files' name in pwd
Dir.glob('dir_name/**/*.{avi,m4a}') # Every avi and m4a files, including in sub-directories
Dir["/target_directory/*"]          # Array of files' path + name

Files

File.basename("my_code.rb")

Nuclear csv parsing: never see the dreaded invalid byte sequence error ever again

csv_file = File.read(file)
               .encode("UTF-8", "binary", invalid: :replace, undef: :replace, replace: "")
CSV.parse(csv_file, col_sep: ";", force_quotes: true, encoding: "utf-8")

# Execute unix commands using backticks `. Returns a string
`wc -l line_count.csv`

require "benchmark"

puts Benchmark.measure { "something".capitalize }

iterations = 1_000

Benchmark.bm(iterations) do |bm|
  bm.report "message here" do
    "something".capitalize
  end

  bm.report "another convoluted method" do
    "something"[0].upcase + "something"[1..-1]
  end
end

Benchmark.ips do |x|
  x.report("any?") { Actor.any? }
  x.report("limit(1)") { Actor.limit(1).count }
  x.compare!
end

# Comparison:
#  limit(1):     1213.5 i/s
#      any?:      597.1 i/s - 2.03x  slower

Syntax highlighting of other languages from within ruby code

sql_query = <<-SQL
              SELECT * FROM users
              WHERE is_awesome IS true
            SQL

URI Library

URI.parse("http://www.github.com")