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Class: OpenStruct

Relationships & Source Files
Inherits: Object
Defined in: lib/ostruct.rb

Overview

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.

Class Method Summary

Instance Method Summary

Constructor Details

.new(hash = nil) ⇒ OpenStruct

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">
[ GitHub ] 

  


# File 'lib/ostruct.rb', line 98



def initialize(hash=nil)
  @table = {}
  if hash
    hash.each_pair do |k, v|
      k = k.to_sym
      @table[k] = v
    end
  end
end


  







Class Method Details



  

    .allocate  
  

  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 78



def allocate
  (x = super).instance_variable_set(:@table, {})
  x
end


  







Instance Method Details



  

    #==(other)  
  



  

    

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


  



  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 345



def ==(other)
  return false unless other.kind_of?(OpenStruct)
  @table == other.table
end


  








  

    #[](name)  ⇒ Object   



  

    

Returns the value of an attribute.



require "ostruct"
person = OpenStruct.new("name" => "John Smith", "age" => 70)
person[:age]   # => 70, same as person.age


  



  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 226



def [](name)
  @table[name.to_sym]
end


  








  

    #[]=(name, obj)  ⇒ Object   



  

    

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


  



  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 241



def []=(name, value)
  modifiable[new_ostruct_member(name)] = value
end


  








  

    #delete_field(name)  
  



  

    

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>


  



  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 290



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


  








  

    #dig(name, ...)  ⇒ Object   



  

    

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


  



  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 265



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


  








  

    

      #each_pair {|name, value| ... } ⇒ ostruct 
      #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"]]


  





  


  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 138



def each_pair
  return to_enum(__method__) { @table.size } unless block_given?
  @table.each_pair{|p| yield p}
  self
end


  








  

    #eql?(other)  ⇒ Boolean 
  



  

    

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?.


  





  


  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 355



def eql?(other)
  return false unless other.kind_of?(OpenStruct)
  @table.eql?(other.table)
end


  








  

    #freeze  
  

  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 187



def freeze
  @table.each_key {|key| new_ostruct_member(key)}
  super
end


  








  

    #hash  
  



  

    

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.


  



  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 365



def hash
  @table.hash
end


  








  

    #inspect  
    Also known as: #to_s
  



  

    

Returns a string containing a detailed summary of the keys and values.


  



  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 306



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


  








  

    #marshal_dump  
  



  

    

Provides marshalling support for use by the Marshal library.


  



  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 147



def marshal_dump
  @table
end


  








  

    #marshal_load(x)  
  



  

    

Provides marshalling support for use by the Marshal library.


  



  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 154



def marshal_load(x)
  @table = x
end


  








  

    #modifiable   (protected)
  



  

    

Used internally to check if the OpenStruct is able to be modified before granting access to the internal Hash table to be modified.


  



  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 162



def modifiable
  begin
    @modifiable = true
  rescue
    raise RuntimeError, "can't modify frozen #{self.class}", caller(3)
  end
  @table
end


  








  

    #new_ostruct_member(name)   (protected)
  



  

    

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.


  



  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 177



def new_ostruct_member(name)
  name = name.to_sym
  unless singleton_class.method_defined?(name)
    define_singleton_method(name) { @table[name] }
    define_singleton_method("#{name}=") { |x| modifiable[name] = x }
  end
  name
end


  








  

    #to_h  
  



  

    

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" }


  



  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 122



def to_h
  @table.dup
end


  








  

    #to_s  
  



  

    

Alias for #inspect.


  



  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 327



alias :to_s :inspect