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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.

Constant Summary

Class Method Summary

Instance Attribute 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 91



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


  







Dynamic Method Handling

  

    This class handles dynamic methods through the method_missing method




  

    #method_missing(mid, *args)  
  

  

    This method is for internal use only.
  

  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 198



def method_missing(mid, *args) # :nodoc:
  len = args.length
  if mname = mid[/.*(?==\z)/m]
    if len != 1
      raise ArgumentError, "wrong number of arguments (#{len} for 1)", caller(1)
    end
    modifiable?[new_ostruct_member!(mname)] = args[0]
  elsif len == 0 # and /\A[a-z_]\w*\z/ =~ mid #
    if @table.key?(mid)
      new_ostruct_member!(mid) unless frozen?
      @table[mid]
    end
  else
    begin
      super
    rescue NoMethodError => err
      err.backtrace.shift
      raise
    end
  end
end


  







Instance Attribute Details



  

    #modifiable   (readonly, protected)
  

  

    This method is for internal use only.
  



  

    

Alias for #modifiable?.


  



  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 166



alias modifiable modifiable? # :nodoc:


  








  

    #table   (readonly, protected)
    Also known as: #table!
  

  

    This method is for internal use only.
  

  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 328



attr_reader :table # :nodoc:


  








  

    #table!   (readonly)
  



  

    

Alias for #table.


  



  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 330



alias table! table


  







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 230



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 245



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 294



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 269



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 131



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 188



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


  








  

    #initialize_copy(orig)  
  

  

    This method is for internal use only.
  



  

    

Duplicates an OpenStruct object's Hash table.


  



  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 102



def initialize_copy(orig) # :nodoc:
  super
  @table = @table.dup
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 310



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


  








  

    #marshal_dump  
  



  

    

Provides marshalling support for use by the Marshal library.


  



  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 140



def marshal_dump
  @table
end


  








  

    #marshal_load(x)  
  



  

    

Provides marshalling support for use by the Marshal library.


  



  [ GitHub ]


  

  


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



def marshal_load(x)
  @table = x
end


  








  

    #modifiable?  ⇒ Boolean  (readonly, private)
    Also known as: #modifiable
  

  

    This method is for internal use only.
  



  

    

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 155



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


  








  

    #new_ostruct_member(name)   (protected)
  

  

    This method is for internal use only.
  



  

    

Alias for #new_ostruct_member!.


  



  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 185



alias new_ostruct_member new_ostruct_member! # :nodoc:


  








  

    #new_ostruct_member!(name)   (private)
    Also known as: #new_ostruct_member
  

  

    This method is for internal use only.
  



  

    

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 174



def new_ostruct_member!(name) # :nodoc:
  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


  








  

    #respond_to_missing?(mid, include_private = false)  ⇒ Boolean 
  

  

    This method is for internal use only.
  



  

    
  





  


  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 193



def respond_to_missing?(mid, include_private = false) # :nodoc:
  mname = mid.to_s.chomp("=").to_sym
  @table&.key?(mname) || super
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 115



def to_h
  @table.dup
end


  








  

    #to_s  
  



  

    

Alias for #inspect.


  



  [ GitHub ]


  

  


# File 'lib/ostruct.rb', line 326



alias :to_s :inspect