Tenderlove Making

TIL: It's OK to return nil from to_ary

Jun 28, 2011 @ 4:08 pm

tl;dr: You can return nil from to_ary and to_a.

class Item
  def respond_to?(name, visibility = false)
    p "respond to: #{name}"
    false # we don't respond to anything!!
  end

  def method_missing(name, *args)
    p "method missing: #{name}"
    super # if something?
    # do something else
  end
end

[[Item.new]].flatten

[aaron@higgins ~]$ ruby -d test.rb
Exception `LoadError' at /Users/aaron/.local/lib/ruby/site_ruby/1.9.1/rubygems.rb:1215 - cannot load such file -- rubygems/defaults/operating_system
Exception `LoadError' at /Users/aaron/.local/lib/ruby/site_ruby/1.9.1/rubygems.rb:1224 - cannot load such file -- rubygems/defaults/ruby
"method missing: to_ary"
Exception `NoMethodError' at test.rb:9 - undefined method `to_ary' for #<Item:0x00000101079e80>
"respond to: to_ary"
[aaron@higgins ~]$

class Item
  def respond_to?(name, visibility = false)
    p "respond to: #{name}"
    false # we don't respond to anything!!
  end

  def method_missing(name, *args)
    p "method missing: #{name}"
    super # if something?
    # do something else
  end

  private
  def to_ary
    nil
  end
end

[[Item.new]].flatten

[aaron@higgins ~]$ ruby -d test.rb
Exception `LoadError' at /Users/aaron/.local/lib/ruby/site_ruby/1.9.1/rubygems.rb:1215 - cannot load such file -- rubygems/defaults/operating_system
Exception `LoadError' at /Users/aaron/.local/lib/ruby/site_ruby/1.9.1/rubygems.rb:1224 - cannot load such file -- rubygems/defaults/ruby
[aaron@higgins ~]$

Array(Item.new)

class Item
  def respond_to?(name, visibility = false)
    p "respond to: #{name}"
    false # we don't respond to anything!!
  end

  def method_missing(name, *args)
    p "method missing: #{name}"
    super # if something?
    # do something else
  end

  private
  def to_ary
    nil
  end
  alias :to_a :to_ary
end

[[Item.new]].flatten
Array(Item.new)
« go back