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.
Examples
require "ostruct" person = OpenStruct.new person.name = "John Smith" person.age = 70 person.name # => "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 = 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. ()[]*) 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 remove the attribute.
first_pet = OpenStruct.new(:name => "Rowdy", :owner => "John Smith") second_pet = OpenStruct.new(:name => "Rowdy") first_pet.owner = nil 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
Implementation
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.
# File tmp/rubies/ruby-2.4.10/ext/json/lib/json/add/ostruct.rb, line 11
def self.json_create(object)
new(object['t'] || object[:t])
end
# File tmp/rubies/ruby-2.4.10/lib/ostruct.rb, line 91
def initialize(hash=nil)
@table = {}
if hash
hash.each_pair do |k, v|
k = k.to_sym
@table[k] = v
end
end
end
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", :capital => "Canberra" } data = OpenStruct.new(hash) data # => #<OpenStruct country="Australia", capital="Canberra">
# File tmp/rubies/ruby-2.4.10/lib/ostruct.rb, line 347
def ==(other)
return false unless other.kind_of?(OpenStruct)
@table == other.table!
end
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.
require "ostruct" 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
# File tmp/rubies/ruby-2.4.10/lib/ostruct.rb, line 227
def [](name)
@table[name.to_sym]
end
Returns the value of an attribute.
require "ostruct" person = OpenStruct.new("name" => "John Smith", "age" => 70) person[:age] # => 70, same as person.age
# File tmp/rubies/ruby-2.4.10/lib/ostruct.rb, line 242
def []=(name, value)
modifiable?[new_ostruct_member!(name)] = value
end
Sets the value of an attribute.
require "ostruct" person = OpenStruct.new("name" => "John Smith", "age" => 70) person[:age] = 42 # equivalent to person.age = 42 person.age # => 42
# File tmp/rubies/ruby-2.4.10/ext/json/lib/json/add/ostruct.rb, line 17
def as_json(*)
klass = self.class.name
klass.to_s.empty? and raise JSON::JSONError, "Only named structs are supported!"
{
JSON.create_id => klass,
't' => table,
}
end
Returns a hash, that will be turned into a JSON object and represent this object.
# File tmp/rubies/ruby-2.4.10/lib/ostruct.rb, line 291
def delete_field(name)
sym = name.to_sym
begin
singleton_class.__send__(:remove_method, sym, "#{sym}=")
rescue NameError
end
@table.delete(sym) do
raise NameError.new("no field `#{sym}' in #{self}", sym)
end
end
Removes the named field from the object. Returns the value that the field contained if it was defined.
require "ostruct" 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.pension = nil person # => #<OpenStruct name="John", pension=nil>
# File tmp/rubies/ruby-2.4.10/lib/ostruct.rb, line 266
def dig(name, *names)
begin
name = name.to_sym
rescue NoMethodError
raise TypeError, "#{name} is not a symbol nor a string"
end
@table.dig(name, *names)
end
Extracts the nested value specified by the sequence of name objects by calling dig at each step, returning nil if any intermediate step is nil.
require "ostruct" address = OpenStruct.new("city" => "Anytown NC", "zip" => 12345) person = OpenStruct.new("name" => "John Smith", "address" => address) person.dig(:address, "zip") # => 12345 person.dig(:business_address, "zip") # => nil data = OpenStruct.new(:array => [1, [2, 3]]) data.dig(:array, 1, 0) # => 2 data.dig(:array, 0, 0) # TypeError: Integer does not have #dig method
# File tmp/rubies/ruby-2.4.10/lib/ostruct.rb, line 131
def each_pair
return to_enum(__method__) { @table.size } unless block_given?
@table.each_pair{|p| yield p}
self
end
Yields all attributes (as symbols) along with the corresponding values or returns an enumerator if no block is given.
require "ostruct" data = OpenStruct.new("country" => "Australia", :capital => "Canberra") data.each_pair.to_a # => [[:country, "Australia"], [:capital, "Canberra"]]
# File tmp/rubies/ruby-2.4.10/lib/ostruct.rb, line 357
def eql?(other)
return false unless other.kind_of?(OpenStruct)
@table.eql?(other.table!)
end
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 tmp/rubies/ruby-2.4.10/lib/ostruct.rb, line 188
def freeze
@table.each_key {|key| new_ostruct_member!(key)}
super
end
# File tmp/rubies/ruby-2.4.10/lib/ostruct.rb, line 367
def hash
@table.hash
end
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?).
See also Object#hash.
# File tmp/rubies/ruby-2.4.10/lib/ostruct.rb, line 307
def inspect
str = "#<#{self.class}"
ids = (Thread.current[InspectKey] ||= [])
if ids.include?(object_id)
return str << ' ...>'
end
ids << object_id
begin
first = true
for k,v in @table
str << "," unless first
first = false
str << " #{k}=#{v.inspect}"
end
return str << '>'
ensure
ids.pop
end
end
Returns a string containing a detailed summary of the keys and values.
# File tmp/rubies/ruby-2.4.10/lib/ostruct.rb, line 140
def marshal_dump
@table
end
Provides marshalling support for use by the Marshal library.
# File tmp/rubies/ruby-2.4.10/lib/ostruct.rb, line 147
def marshal_load(x)
@table = x
end
Provides marshalling support for use by the Marshal library.
# File tmp/rubies/ruby-2.4.10/lib/ostruct.rb, line 115
def to_h
@table.dup
end
Converts the OpenStruct to a hash with keys representing each attribute (as symbols) and their corresponding values.
require "ostruct" data = OpenStruct.new("country" => "Australia", :capital => "Canberra") data.to_h # => {:country => "Australia", :capital => "Canberra" }
# File tmp/rubies/ruby-2.4.10/ext/json/lib/json/add/ostruct.rb, line 28
def to_json(*args)
as_json.to_json(*args)
end
Stores class name (OpenStruct) with this struct’s values v as a JSON string.