class OpenStruct

OpenStruct serialization/deserialization

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
person.pension = 300

puts     # -> "John Smith"
puts person.age      # -> 70
puts person.address  # -> nil

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

australia = => "Australia", :population => 20_000_000)
p australia   # -> <OpenStruct country="Australia" population=20000000>

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

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

data_point = => true)
data_point.queued?                       # -> true
data_point.queued?                       # -> false

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

first_pet = => 'Rowdy', :owner => 'John Smith')
first_pet.owner = nil
second_pet = => 'Rowdy')

first_pet == second_pet   # -> false

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 method method_missing and define_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.

Public Class Methods

json_create(object) click to toggle source

Deserializes JSON string by constructing new Struct object with values v serialized by to_json.

# File ext/json/lib/json/add/ostruct.rb, line 11
def self.json_create(object)
  new(object['t'] || object[:t])
new(hash=nil) click to toggle source

Creates a new OpenStruct object. By default, the resulting OpenStruct object will have no attributes.

The optional hash, if given, will generate attributes and values (can be a Hash, an OpenStruct or a Struct). For example:

require 'ostruct'
hash = { "country" => "Australia", :population => 20_000_000 }
data =

p data        # -> <OpenStruct country="Australia" population=20000000>
# File lib/ostruct.rb, line 87
def initialize(hash=nil)
  @table = {}
  if hash
    hash.each_pair do |k, v|
      k = k.to_sym
      @table[k] = v

Public Instance Methods

==(other) click to toggle source

Compares this object and other for equality. An OpenStruct is equal to other when other is an OpenStruct and the two objects' Hash tables are equal.

# File lib/ostruct.rb, line 265
def ==(other)
  return false unless other.kind_of?(OpenStruct)
  @table == other.table
[](name) click to toggle source

Returns the value of a member.

person ='name' => 'John Smith', 'age' => 70)
person[:age] # => 70, same as ostruct.age
# File lib/ostruct.rb, line 198
def [](name)
[]=(name, value) click to toggle source

Sets the value of a member.

person ='name' => 'John Smith', 'age' => 70)
person[:age] = 42 # => equivalent to ostruct.age = 42
person.age # => 42
# File lib/ostruct.rb, line 209
def []=(name, value)
  modifiable[new_ostruct_member(name)] = value
as_json(*) click to toggle source

Returns a hash, that will be turned into a JSON object and represent this object.

# File ext/json/lib/json/add/ostruct.rb, line 17
def as_json(*)
  klass =
  klass.to_s.empty? and raise JSON::JSONError, "Only named structs are supported!"
    JSON.create_id => klass,
    't'            => table,
delete_field(name) click to toggle source

Remove the named field from the object. Returns the value that the field contained if it was defined.

require 'ostruct'

person ='name' => 'John Smith', 'age' => 70)

person.delete_field('name')  # => 'John Smith'
# File lib/ostruct.rb, line 223
def delete_field(name)
  sym = name.to_sym
  singleton_class.__send__(:remove_method, sym, "#{sym}=")
  @table.delete sym
each_pair() { |p| ... } click to toggle source

Yields all attributes (as a symbol) along with the corresponding values or returns an enumerator if not block is given. Example:

require 'ostruct'
data ="country" => "Australia", :population => 20_000_000)
data.each_pair.to_a  # => [[:country, "Australia"], [:population, 20000000]]
# File lib/ostruct.rb, line 127
def each_pair
  return to_enum(__method__) { @table.size } unless block_given?
  @table.each_pair{|p| yield p}
eql?(other) click to toggle source

Compares this object and other for equality. An OpenStruct is eql? to other when other is an OpenStruct and the two objects' Hash tables are eql?.

# File lib/ostruct.rb, line 275
def eql?(other)
  return false unless other.kind_of?(OpenStruct)
hash() click to toggle source

Compute a hash-code for this OpenStruct. Two hashes with the same content will have the same hash code (and will be eql?).

# File lib/ostruct.rb, line 283
def hash
initialize_copy(orig) click to toggle source

Duplicate an OpenStruct object members.

Calls superclass method
# File lib/ostruct.rb, line 99
def initialize_copy(orig)
  @table = @table.dup
  @table.each_key{|key| new_ostruct_member(key)}
inspect() click to toggle source

Returns a string containing a detailed summary of the keys and values.

# File lib/ostruct.rb, line 234
def inspect
  str = "#<#{self.class}"

  ids = (Thread.current[InspectKey] ||= [])
  if ids.include?(object_id)
    return str << ' ...>'

  ids << object_id
    first = true
    for k,v in @table
      str << "," unless first
      first = false
      str << " #{k}=#{v.inspect}"
    return str << '>'
Also aliased as: to_s
marshal_dump() click to toggle source

Provides marshalling support for use by the Marshal library.

# File lib/ostruct.rb, line 135
def marshal_dump
marshal_load(x) click to toggle source

Provides marshalling support for use by the Marshal library.

# File lib/ostruct.rb, line 142
def marshal_load(x)
  @table = x
  @table.each_key{|key| new_ostruct_member(key)}
to_h() click to toggle source

Converts the OpenStruct to a hash with keys representing each attribute (as symbols) and their corresponding values Example:

require 'ostruct'
data ="country" => "Australia", :population => 20_000_000)
data.to_h   # => {:country => "Australia", :population => 20000000 }
# File lib/ostruct.rb, line 114
def to_h
to_json(*args) click to toggle source

Stores class name (OpenStruct) with this struct's values v as a JSON string.

# File ext/json/lib/json/add/ostruct.rb, line 28
def to_json(*args)
Alias for: inspect

Protected Instance Methods

modifiable() click to toggle source

Used internally to check if the OpenStruct is able to be modified before granting access to the internal Hash table to be modified.

# File lib/ostruct.rb, line 151
def modifiable
    @modifiable = true
    raise RuntimeError, "can't modify frozen #{self.class}", caller(3)
new_ostruct_member(name) click to toggle source

Used internally to defined properties on the OpenStruct. It does this by using the metaprogramming function define_singleton_method for both the getter method and the setter method.

# File lib/ostruct.rb, line 166
def new_ostruct_member(name)
  name = name.to_sym
  unless respond_to?(name)
    define_singleton_method(name) { @table[name] }
    define_singleton_method("#{name}=") { |x| modifiable[name] = x }