Class: OpenStruct

Inherits:
Object
  • Object
show all
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 collapse

InspectKey =

:nodoc:

:__inspect_key__

Instance Method Summary collapse

Constructor Details

#initialize(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">



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# 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) ⇒ Object

:nodoc:



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# File 'lib/ostruct.rb', line 199

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 Method Details

#==(other) ⇒ Object

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



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# File 'lib/ostruct.rb', line 346

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

#[](name) ⇒ Object

:call-seq:

ostruct[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



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# File 'lib/ostruct.rb', line 231

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

#[]=(name, value) ⇒ Object

:call-seq:

ostruct[name] = obj  -> obj

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



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# File 'lib/ostruct.rb', line 246

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

#delete_field(name) ⇒ Object

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>



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# File 'lib/ostruct.rb', line 295

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, *names) ⇒ Object

:call-seq:

ostruct.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



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# File 'lib/ostruct.rb', line 270

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 ⇒ Object

:call-seq:

ostruct.each_pair {|name, value| block }  -> ostruct
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"]]



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# 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?.

Returns:

  • (Boolean) 


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# File 'lib/ostruct.rb', line 356

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

#freeze ⇒ Object 



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# File 'lib/ostruct.rb', line 189

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

#hash ⇒ Object

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.



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# File 'lib/ostruct.rb', line 366

def hash
  @table.hash
end

#initialize_copy(orig) ⇒ Object

Duplicates an OpenStruct object’s Hash table.



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

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

#inspect ⇒ Object Also known as: to_s

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



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# File 'lib/ostruct.rb', line 311

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 ⇒ Object

Provides marshalling support for use by the Marshal library.



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

def marshal_dump
  @table
end

#marshal_load(x) ⇒ Object

Provides marshalling support for use by the Marshal library.



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

def marshal_load(x)
  @table = x
end

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

:nodoc:

Returns:

  • (Boolean) 


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# File 'lib/ostruct.rb', line 194

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

#to_h ⇒ Object

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" }



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# File 'lib/ostruct.rb', line 115

def to_h
  @table.dup
end