ActiveSupport、Array#in_groups_of
まんま
>> require "rubygems" => true >> require "active_support" => true >> %w(1 2 3 4 5 6 7).in_groups_of(3) {|g| p g} ["1", "2", "3"] ["4", "5", "6"] ["7", nil, nil] => nil >> %w(1 2 3).in_groups_of(2, ' ') {|g| p g} ["1", "2"] ["3", " "] => nil >> %w(1 2 3).in_groups_of(2, false) {|g| p g} ["1", "2"] ["3"] => nil