Group By Intro

group_by builds a hash where each key points to matching values.

group_by_intro.rb

split_at = 
numbers = [2, 4, 5, 8]

groups = numbers.group_by do |number|
  number >= split_at ? "large" : "small"
end

small = groups.fetch("small", [])
large = groups.fetch("large", [])

puts "split_at=#{split_at}"
puts "small=#{small.join(",")}"
puts "large=#{large.join(",")}"

split_at = 
numbers = [2, 4, 5, 8]

groups = numbers.group_by do |number|
  number >= split_at ? "large" : "small"
end

small = groups.fetch("small", [])
large = groups.fetch("large", [])

puts "split_at=#{split_at}"
puts "small=#{small.join(",")}"
puts "large=#{large.join(",")}"

split_at = 
numbers = [2, 4, 5, 8]

groups = numbers.group_by do |number|
  number >= split_at ? "large" : "small"
end

small = groups.fetch("small", [])
large = groups.fetch("large", [])

puts "split_at=#{split_at}"
puts "small=#{small.join(",")}"
puts "large=#{large.join(",")}"

group by `group_by` chooses a key for each item and collects items with the same key.