Object
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.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
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.
frozen_string_literal: true
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 ostruct.rb, line 93
def initialize(hash=nil)
@table = {}
if hash
hash.each_pair do |k, v|
k = k.to_sym
@table[k] = v
end
end
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 ostruct.rb, line 355
def ==(other)
return false unless other.kind_of?(OpenStruct)
@table == other.table!
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 ostruct.rb, line 240
def [](name)
@table[name.to_sym]
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 ostruct.rb, line 255
def []=(name, value)
modifiable?[new_ostruct_member!(name)] = value
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 ostruct.rb, line 304
def delete_field(name)
sym = name.to_sym
begin
singleton_class.remove_method(sym, "#{sym}=")
rescue NameError
end
@table.delete(sym) do
raise NameError.new("no field `#{sym}' in #{self}", sym)
end
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 ostruct.rb, line 279
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
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 ostruct.rb, line 146
def each_pair
return to_enum(__method__) { @table.size } unless block_given?
@table.each_pair{|p| yield p}
self
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 ostruct.rb, line 365
def eql?(other)
return false unless other.kind_of?(OpenStruct)
@table.eql?(other.table!)
end
# File ostruct.rb, line 196
def freeze
@table.each_key {|key| new_ostruct_member!(key)}
super
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 ostruct.rb, line 375
def hash
@table.hash
end
Returns a string containing a detailed summary of the keys and values.
# File ostruct.rb, line 320
def inspect
ids = (Thread.current[InspectKey] ||= [])
if ids.include?(object_id)
detail = ' ...'
else
ids << object_id
begin
detail = @table.map do |key, value|
" #{key}=#{value.inspect}"
end.join(',')
ensure
ids.pop
end
end
['#<', self.class, detail, '>'].join
end
Provides marshalling support for use by the Marshal library.
# File ostruct.rb, line 155
def marshal_dump
@table
end
Provides marshalling support for use by the Marshal library.
# File ostruct.rb, line 162
def marshal_load(x)
@table = x
end
Converts the OpenStruct to a hash with keys representing each attribute (as symbols) and their corresponding values.
If a block is given, the results of the block on each pair of the receiver will be used as pairs.
require "ostruct" data = OpenStruct.new("country" => "Australia", :capital => "Canberra") data.to_h # => {:country => "Australia", :capital => "Canberra" } data.to_h {|name, value| [name.to_s, value.upcase] } # => {"country" => "AUSTRALIA", "capital" => "CANBERRA" }
# File ostruct.rb, line 126
def to_h(&block)
if block_given?
@table.to_h(&block)
else
@table.dup
end
end