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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

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 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

==(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 ostruct.rb, line 350
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 ostruct.rb, line 230
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 ostruct.rb, line 245
def []=(name, value)
  modifiable?[new_ostruct_member!(name)] = value
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 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 click to toggle source

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 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| 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 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 ostruct.rb, line 360
def eql?(other)
  return false unless other.kind_of?(OpenStruct)
  @table.eql?(other.table!)
end
            
freeze() click to toggle source
 
               # File ostruct.rb, line 188
def freeze
  @table.each_key {|key| new_ostruct_member!(key)}
  super
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 ostruct.rb, line 370
def hash
  @table.hash
end
            
inspect() click to toggle source

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

 
               # File ostruct.rb, line 310
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 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 ostruct.rb, line 147
def marshal_load(x)
  @table = x
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 ostruct.rb, line 115
def to_h
  @table.dup
end
            
to_s() click to toggle source
Alias for: inspect