A Struct is a convenient way to bundle a number of attributes together, using accessor methods, without having to write an explicit class.

The Struct class generates new subclasses that hold a set of members and their values. For each member a reader and writer method is created similar to Module#attr_accessor.

Customer =, :address) do
  def greeting
    "Hello #{name}!"

dave ="Dave", "123 Main")     #=> "Dave"
dave.greeting #=> "Hello Dave!"

See Struct::new for further examples of creating struct subclasses and instances.

In the method descriptions that follow, a “member” parameter refers to a struct member which is either a quoted string ("name") or a Symbol (:name).

Struct Reference


Part of standard library. You need to require 'ostruct' before using.

An OpenStruct is a data structure, similar to a Hash, that allows the definition of arbitrary attributes with their accompanying values. This is accomplished by using Ruby’s metaprogramming to define methods on the class itself.


require "ostruct"

person = = "John Smith"
person.age  = 70      # => "John Smith"
person.age       # => 70
person.address   # => nil

An OpenStruct employs a Hash internally to store the attributes and values and can even be initialized with one:

australia = => "Australia", :capital => "Canberra")
  # => #<OpenStruct country="Australia", capital="Canberra">

Hash keys with spaces or characters that could normally not be used for method calls (e.g. ()[]*) will not be immediately available on the OpenStruct object as a method for retrieval or assignment, but can still be reached through the Object#send method.

measurements ="length (in inches)" => 24)
measurements.send("length (in inches)")   # => 24

message = => true)
message.queued?                           # => true
message.send("queued?=", false)
message.queued?                           # => false

Removing the presence of an attribute requires the execution of the delete_field method as setting the property value to nil will not remove the attribute.

first_pet  = => "Rowdy", :owner => "John Smith")
second_pet = => "Rowdy")

first_pet.owner = nil
first_pet                 # => #<OpenStruct name="Rowdy", owner=nil>
first_pet == second_pet   # => false

first_pet                 # => #<OpenStruct name="Rowdy">
first_pet == second_pet   # => true


An OpenStruct utilizes Ruby’s method lookup structure to find and define the necessary methods for properties. This is accomplished through the methods method_missing and define_singleton_method.

This should be a consideration if there is a concern about the performance of the objects that are created, as there is much more overhead in the setting of these properties compared to using a Hash or a Struct.

OpenStruct Reference