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