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

json_create(object) click to toggle source

Deserializes JSON string by constructing new Struct object with values v serialized by to_json.

# File ext/json/lib/json/add/ostruct.rb, line 10
def self.json_create(object)
  new(object['t'] || object[:t])
end
new(hash=nil) click to toggle source

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

==(other) click to toggle source

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
ostruct[name] → object click to toggle source

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
ostruct[name] = obj → obj click to toggle source

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
as_json(*) click to toggle source

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
delete_field(name) click to toggle source

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
each_pair {|name, value| block } → ostruct click to toggle source
each_pair → Enumerator

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
eql?(other) click to toggle source

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
hash() click to toggle source

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
inspect() click to toggle source

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
Also aliased as: to_s
marshal_dump() click to toggle source

Provides marshalling support for use by the Marshal library.

# File lib/ostruct.rb, line 140
def marshal_dump
  @table
end
marshal_load(x) click to toggle source

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
to_h() click to toggle source

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
to_json(*args) click to toggle source

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
to_s()
Alias for: inspect

Protected Instance Methods

modifiable() click to toggle source

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
new_ostruct_member(name) click to toggle source

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