class OpenStruct
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
.
Public Class Methods
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 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
Public Instance Methods
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 lib/ostruct.rb, line 347 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 lib/ostruct.rb, line 227 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 lib/ostruct.rb, line 242 def []=(name, value) modifiable?[new_ostruct_member!(name)] = value end
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 = self.class.name klass.to_s.empty? and raise JSON::JSONError, "Only named structs are supported!" { JSON.create_id => klass, 't' => table, } 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 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
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 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
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 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
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 357 def eql?(other) return false unless other.kind_of?(OpenStruct) @table.eql?(other.table!) end
Object#freeze
# File lib/ostruct.rb, line 188 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 lib/ostruct.rb, line 367 def hash @table.hash end
Returns a string containing a detailed summary of the keys and values.
# File 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
Provides marshalling support for use by the Marshal
library.
# File lib/ostruct.rb, line 140 def marshal_dump @table end
Provides marshalling support for use by the Marshal
library.
# File lib/ostruct.rb, line 147 def marshal_load(x) @table = x 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 lib/ostruct.rb, line 115 def to_h @table.dup end
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) as_json.to_json(*args) end