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 89 def initialize(hash=nil) @table = {} if hash hash.each_pair do |k, v| k = k.to_sym @table[k] = v new_ostruct_member(k) 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 293 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 208 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 223 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 16 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 243 def delete_field(name) sym = name.to_sym singleton_class.__send__(:remove_method, sym, "#{sym}=") @table.delete sym 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 303 def eql?(other) return false unless other.kind_of?(OpenStruct) @table.eql?(other.table) 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 313 def hash @table.hash end
Returns a string containing a detailed summary of the keys and values.
# File lib/ostruct.rb, line 254 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 @table.each_key{|key| new_ostruct_member(key)} 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 27 def to_json(*args) as_json.to_json(*args) end
Protected Instance Methods
Used internally to check if the OpenStruct is able to be modified before granting access to the internal Hash table to be modified.
# File lib/ostruct.rb, line 156 def modifiable begin @modifiable = true rescue raise RuntimeError, "can't modify frozen #{self.class}", caller(3) end @table end
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.
# File lib/ostruct.rb, line 171 def new_ostruct_member(name) name = name.to_sym unless respond_to?(name) define_singleton_method(name) { @table[name] } define_singleton_method("#{name}=") { |x| modifiable[name] = x } end name end