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  • ostruct.rb

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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 = OpenStruct.new
person.name    = "John Smith"
person.age     = 70
person.pension = 300

puts person.name     # -> "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 = OpenStruct.new(:country => "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 = OpenStruct.new("length (in inches)" => 24)
measurements.send("length (in inches)")  # -> 24

data_point = OpenStruct.new(:queued? => 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 = OpenStruct.new(:name => 'Rowdy', :owner => 'John Smith')
first_pet.owner = nil
second_pet = OpenStruct.new(:name => 'Rowdy')

first_pet == second_pet   # -> false

first_pet == second_pet   # -> true


An OpenStruct utilizes Ruby's method lookup structure to and 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

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. For example:

require 'ostruct'
hash = { "country" => "Australia", :population => 20_000_000 }
data = OpenStruct.new(hash)

p data        # -> <OpenStruct country="Australia" population=20000000>
               # File ostruct.rb, line 86
def initialize(hash=nil)
  @table = {}
  if hash
    for k,v in hash
      @table[k.to_sym] = 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 object's Hash tables are equal.

               # File ostruct.rb, line 232
def ==(other)
  return false unless(other.kind_of?(OpenStruct))
  return @table == other.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 = OpenStruct.new('name' => 'John Smith', 'age' => 70)

person.delete_field('name')  # => 'John Smith'
               # File ostruct.rb, line 190
def delete_field(name)
  sym = name.to_sym
  singleton_class.__send__(:remove_method, sym, "#{name}=")
  @table.delete sym
initialize_copy(orig) click to toggle source

Duplicate an OpenStruct object members.

               # File ostruct.rb, line 97
def initialize_copy(orig)
  @table = @table.dup
inspect() click to toggle source

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

               # File ostruct.rb, line 201
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. Returning the underlying Hash table that contains the functions defined as the keys and the values assigned to them.

require 'ostruct'

person = OpenStruct.new
person.name = 'John Smith'
person.age  = 70

person.marshal_dump # => { :name => 'John Smith', :age => 70 }
               # File ostruct.rb, line 115
def marshal_dump
marshal_load(x) click to toggle source

Provides marshalling support for use by the Marshal library. Accepting a Hash of keys and values which will be used to populate the internal table

require 'ostruct'

event = OpenStruct.new
hash = { 'time' => Time.now, 'title' => 'Birthday Party' }
event.title # => 'Birthday Party'
               # File ostruct.rb, line 130
def marshal_load(x)
  @table = x
  @table.each_key{|key| new_ostruct_member(key)}
new_ostruct_member(name) click to toggle source

#new_ostruct_member is used internally to defined properties on the OpenStruct. It does this by using the metaprogramming function define_method for both the getter method and the setter method.

               # File ostruct.rb, line 154
def new_ostruct_member(name)
  name = name.to_sym
  unless self.respond_to?(name)
    class << self; self; end.class_eval do
      define_method(name) { @table[name] }
      define_method("#{name}=") { |x| modifiable[name] = x }
to_s() click to toggle source
Alias for: inspect

Protected Instance Methods

modifiable() click to toggle source

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

               # File ostruct.rb, line 139
def modifiable
    @modifiable = true
    raise TypeError, "can't modify frozen #{self.class}", caller(3)