Example of Grouping with Ruby 2+ by using: group_by, Array, collection, subgroup

group_example.rb

# Example of Grouping with Ruby
#  features: group_by, Array, collection, subgroup 

# Here the collection 
#  where #{group_name}_#{subgroup0}_#{subgroup1}...
collection = ['AA_A_B_C', 'BB_A_B_C', 'CC_A_B_C', 'AA_A_A_A', 'BB_B_B_B']

# To range allow to convert 
#  a subgroup to a range
#
# | A = 0:1
# | B = 1:3
# | C = 3:5 
#
def to_range(name)
  case name
    when 'A'
      [0,1]
    when 'B'
      [1,3]
    when 'C'
      [3,5]
    else
      raise "Error: #{name} "
  end
end

# Group element by startting
grouped = collection.group_by { |it| it[0..2] }

raise 'Expect 3 group' unless grouped.size == 3

# Iterate on the group
grouped.each do |group_name, values|
  # Display group name
  puts group_name.gsub('_', '') 
  values.each do |value|
    puts '---' # Add spacer between each subgroup
    # Display a sub group
    value[2..value.size-1].split('_').each { |name|
      next if name.size == 0
      range = to_range(name) # Map each term
      puts "- #{name} : #{range.first}:#{range.last}" # Display the mapping
    }
  end
  puts ''
end