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  • ruby-3.1.2/ext/json/lib/json/add/ostruct.rb
  • ruby-3.1.2/lib/ostruct.rb

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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 or using [].

measurements = OpenStruct.new("length (in inches)" => 24)
measurements[:"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

Ractor compatibility: A frozen OpenStruct with shareable values is itself shareable.

Caveats

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. Creating an open struct from a small Hash and accessing a few of the entries can be 200 times slower than accessing the hash directly.

This is a potential security issue; building OpenStruct from untrusted user data (e.g. JSON web request) may be susceptible to a “symbol denial of service” attack since the keys create methods and names of methods are never garbage collected.

This may also be the source of incompatibilities between Ruby versions:

o = OpenStruct.new
o.then # => nil in Ruby < 2.6, enumerator for Ruby >= 2.6

Builtin methods may be overwritten this way, which may be a source of bugs or security issues:

o = OpenStruct.new
o.methods # => [:to_h, :marshal_load, :marshal_dump, :each_pair, ...
o.methods = [:foo, :bar]
o.methods # => [:foo, :bar]

To help remedy clashes, OpenStruct uses only protected/private methods ending with ! and defines aliases for builtin public methods by adding a !:

o = OpenStruct.new(make: 'Bentley', class: :luxury)
o.class # => :luxury
o.class! # => OpenStruct

It is recommended (but not enforced) to not use fields ending in !; Note that a subclass' methods may not be overwritten, nor can OpenStruct's own methods ending with !.

For all these reasons, consider not using OpenStruct at all.

Constants

VERSION

Public Class Methods

json_create(object) click to toggle source

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

 
               # File ruby-3.1.2/ext/json/lib/json/add/ostruct.rb, line 11
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 ruby-3.1.2/lib/ostruct.rb, line 126
def initialize(hash=nil)
  if hash
    update_to_values!(hash)
  else
    @table = {}
  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 ruby-3.1.2/lib/ostruct.rb, line 411
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, or nil if there is no such attribute.

require "ostruct"
person = OpenStruct.new("name" => "John Smith", "age" => 70)
person[:age]   # => 70, same as person.age
 
               # File ruby-3.1.2/lib/ostruct.rb, line 291
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 ruby-3.1.2/lib/ostruct.rb, line 306
def []=(name, value)
  name = name.to_sym
  new_ostruct_member!(name)
  @table[name] = value
end
            
Also aliased as: set_ostruct_member_value!
as_json(*) click to toggle source

Returns a hash, that will be turned into a JSON object and represent this object.

 
               # File ruby-3.1.2/ext/json/lib/json/add/ostruct.rb, line 17
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 and returns the value the field contained if it was defined. You may optionally provide a block. If the field is not defined, the result of the block is returned, or a NameError is raised if no block was given.

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>

person.delete_field('number')  # => NameError

person.delete_field('number') { 8675_309 } # => 8675309
 
               # File ruby-3.1.2/lib/ostruct.rb, line 359
def delete_field(name)
  sym = name.to_sym
  begin
    singleton_class.remove_method(sym, "#{sym}=")
  rescue NameError
  end
  @table.delete(sym) do
    return yield if block_given!
    raise! NameError.new("no field `#{sym}' in #{self}", sym)
  end
end
            
dig(name, *identifiers) → object click to toggle source

Finds and returns the object in nested objects that is specified by name and identifiers. The nested objects may be instances of various classes. See Dig Methods.

Examples:

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
 
               # File ruby-3.1.2/lib/ostruct.rb, line 328
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 ruby-3.1.2/lib/ostruct.rb, line 199
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 ruby-3.1.2/lib/ostruct.rb, line 421
def eql?(other)
  return false unless other.kind_of?(OpenStruct)
  @table.eql?(other.table!)
end
            
freeze() click to toggle source
 
               # File ruby-3.1.2/lib/ostruct.rb, line 257
def freeze
  @table.freeze
  super
end
            
inspect() click to toggle source

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

 
               # File ruby-3.1.2/lib/ostruct.rb, line 376
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
            
Also aliased as: to_s
to_h(&block) click to toggle source
 
               # File ruby-3.1.2/lib/ostruct.rb, line 170
def to_h(&block)
  if block
    @table.to_h(&block)
  else
    @table.dup
  end
end
            
to_json(*args) click to toggle source

Stores class name (OpenStruct) with this struct's values t as a JSON string.

 
               # File ruby-3.1.2/ext/json/lib/json/add/ostruct.rb, line 28
def to_json(*args)
  as_json.to_json(*args)
end
            
to_s() click to toggle source
Alias for: inspect

Private Instance Methods

set_ostruct_member_value!(name, value) click to toggle source
Alias for: []=