# 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 `t` serialized by `to_json`.

    # File 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 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

### 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 359
    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 244
    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 259
    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 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. 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 308
    def delete_field(name)
      sym = name.to_sym
      begin
        singleton_class.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 lib/ostruct.rb, line 283
    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 lib/ostruct.rb, line 144
    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 369
    def eql?(other)
      return false unless other.kind_of?(OpenStruct)
      @table.eql?(other.table!)
    end

freeze() click to toggle source
Calls superclass method `Object#freeze`

    # File lib/ostruct.rb, line 202
    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 lib/ostruct.rb, line 379
    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 324
    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
marshal_dump() click to toggle source

Provides marshalling support for use by the `Marshal` library.

    # File lib/ostruct.rb, line 153
    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 160
    def marshal_load(x)
      @table = x
    end

to_h → hash click to toggle source
to_h {|name, value| block } → hash

Converts the `OpenStruct` to a hash with keys representing each attribute (as symbols) and their corresponding values.

If a block is given, the results of the block on each pair of the receiver will be used as pairs.

    require "ostruct"
    data = OpenStruct.new("country" => "Australia", :capital => "Canberra")
    data.to_h   # => {:country => "Australia", :capital => "Canberra" }
    data.to_h {|name, value| [name.to_s, value.upcase] }
                # => {"country" => "AUSTRALIA", "capital" => "CANBERRA" }

    # File lib/ostruct.rb, line 124
    def to_h(&block)
      if block_given?
        @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 `v` as a `JSON` string.

    # File ext/json/lib/json/add/ostruct.rb, line 28
    def to_json(*args)
      as_json.to_json(*args)
    end

to_s()
Alias for: inspect