# = ostruct.rb: OpenStruct implementation
# Author:: Yukihiro Matsumoto
# Documentation:: Gavin Sinclair
# OpenStruct allows the creation of data objects with arbitrary attributes.
# See OpenStruct for an example.
# 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
# person = OpenStruct.new
# person.name = "John Smith"
# person.name # => "John Smith"
# person.address # => nil
# An OpenStruct employs a Hash internally to store the attributes and values
# and can even be initialized with one:
# australia = OpenStruct.new(:country => "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. <code>()[]*</code>) 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 = OpenStruct.new("length (in inches)" => 24)
# measurements.send("length (in inches)") # => 24
# message = OpenStruct.new(:queued? => 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
# first_pet = OpenStruct.new(:name => "Rowdy", :owner => "John Smith")
# second_pet = OpenStruct.new(:name => "Rowdy")
# first_pet # => #<OpenStruct name="Rowdy", owner=nil>
# first_pet == second_pet # => false
# first_pet.delete_field(:owner)
# 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.
# 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).
# hash = { "country" => "Australia", :capital => "Canberra" }
# data = OpenStruct.new(hash)
# data # => #<OpenStruct country="Australia", capital="Canberra">
# Duplicates an OpenStruct object's Hash table.
def initialize_copy(orig) # :nodoc:
@table.each_key{|key| new_ostruct_member(key)}
# Converts the OpenStruct to a hash with keys representing
# each attribute (as symbols) and their corresponding values.
# data = OpenStruct.new("country" => "Australia", :capital => "Canberra")
# data.to_h # => {:country => "Australia", :capital => "Canberra" }
# ostruct.each_pair {|name, value| block } -> ostruct
# ostruct.each_pair -> Enumerator
# Yields all attributes (as symbols) along with the corresponding values
# or returns an enumerator if no block is given.
# data = OpenStruct.new("country" => "Australia", :capital => "Canberra")
# data.each_pair.to_a # => [[:country, "Australia"], [:capital, "Canberra"]]
return to_enum(__method__) { @table.size } unless block_given?
@table.each_pair{|p| yield p}
# Provides marshalling support for use by the Marshal library.
# Provides marshalling support for use by the Marshal library.
@table.each_key{|key| new_ostruct_member(key)}
# Used internally to check if the OpenStruct is able to be
# modified before granting access to the internal Hash table to be modified.
raise RuntimeError, "can't modify frozen #{self.class}", caller(3)
# 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.
def new_ostruct_member(name)
define_singleton_method(name) { @table[name] }
define_singleton_method("#{name}=") { |x| modifiable[name] = x }
protected :new_ostruct_member
def method_missing(mid, *args) # :nodoc:
raise ArgumentError, "wrong number of arguments (#{len} for 1)", caller(1)
modifiable[new_ostruct_member(mname)] = args[0]
err = NoMethodError.new "undefined method `#{mid}' for #{self}", mid, args
err.set_backtrace caller(1)
# ostruct[name] -> object
# Returns the value of an attribute.
# person = OpenStruct.new("name" => "John Smith", "age" => 70)
# person[:age] # => 70, same as person.age
# ostruct[name] = obj -> obj
# Sets the value of an attribute.
# person = OpenStruct.new("name" => "John Smith", "age" => 70)
# person[:age] = 42 # equivalent to person.age = 42
modifiable[new_ostruct_member(name)] = value
# Removes the named field from the object. Returns the value that the field
# contained if it was defined.
# person = OpenStruct.new(name: "John", age: 70, pension: 300)
# person.delete_field("age") # => 70
# person # => #<OpenStruct name="John", pension=300>
# Setting the value to +nil+ will not remove the attribute:
# person # => #<OpenStruct name="John", pension=nil>
singleton_class.__send__(:remove_method, sym, "#{sym}=")
InspectKey = :__inspect_key__ # :nodoc:
# Returns a string containing a detailed summary of the keys and values.
ids = (Thread.current[InspectKey] ||= [])
if ids.include?(object_id)
str << " #{k}=#{v.inspect}"
attr_reader :table # :nodoc:
# 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
# first_pet = OpenStruct.new("name" => "Rowdy")
# second_pet = OpenStruct.new(:name => "Rowdy")
# third_pet = OpenStruct.new("name" => "Rowdy", :age => nil)
# first_pet == second_pet # => true
# first_pet == third_pet # => false
return false unless other.kind_of?(OpenStruct)
# 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
return false unless other.kind_of?(OpenStruct)
# Computes a hash code for this OpenStruct.
# Two OpenStruct objects with the same content will have the same hash code
# (and will compare using #eql?).
