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#
# = ostruct.rb: OpenStruct implementation
#
# Author:: Yukihiro Matsumoto
# Documentation:: Gavin Sinclair
#
# OpenStruct allows the creation of data objects with arbitrary attributes.
# See OpenStruct for an example.
#
#
# 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.pension = 300
#
# puts person.name # -> "John Smith"
# puts person.age # -> 70
# puts person.address # -> nil
#
# An OpenStruct employs a Hash internally to store the methods and values and
# can even be initialized with one:
#
# australia = OpenStruct.new(:country => "Australia", :population => 20_000_000)
# p australia # -> <OpenStruct country="Australia" population=20000000>
#
# Hash keys with spaces or characters that would normally not be able to use for
# method calls (e.g. ()[]*) will not be immediately available on the
# OpenStruct object as a method for retrieval or assignment, but can be still be
# reached through the Object#send method.
#
# measurements = OpenStruct.new("length (in inches)" => 24)
# measurements.send("length (in inches)") # -> 24
#
# data_point = OpenStruct.new(:queued? => true)
# data_point.queued? # -> true
# data_point.send("queued?=",false)
# data_point.queued? # -> false
#
# Removing the presence of a method requires the execution the delete_field
# method as setting the property value to +nil+ will not remove the method.
#
# first_pet = OpenStruct.new(:name => 'Rowdy', :owner => 'John Smith')
# first_pet.owner = nil
# second_pet = OpenStruct.new(:name => 'Rowdy')
#
# first_pet == second_pet # -> false
#
# first_pet.delete_field(:owner)
# first_pet == second_pet # -> true
#
#
# == Implementation:
#
# An OpenStruct utilizes Ruby's method lookup structure to and find and define
# the necessary methods for properties. This is accomplished through the method
# method_missing and define_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.
#
class 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.
# For example:
#
# require 'ostruct'
# hash = { "country" => "Australia", :population => 20_000_000 }
# data = OpenStruct.new(hash)
#
# p data # -> <OpenStruct country="Australia" population=20000000>
#
def initialize(hash=nil)
@table = {}
if hash
for k,v in hash
@table[k.to_sym] = v
new_ostruct_member(k)
end
end
end
# Duplicate an OpenStruct object members.
def initialize_copy(orig)
super
@table = @table.dup
@table.each_key{|key| new_ostruct_member(key)}
end
#
# Converts the OpenStruct to a hash with keys representing
# each attribute (as symbols) and their corresponding values
# Example:
#
# require 'ostruct'
# data = OpenStruct.new("country" => "Australia", :population => 20_000_000)
# data.to_h # => {:country => "Australia", :population => 20000000 }
#
def to_h
@table.dup
end
#
# Provides marshalling support for use by the Marshal library. Returning the
# underlying Hash table that contains the functions defined as the keys and
# the values assigned to them.
#
# require 'ostruct'
#
# person = OpenStruct.new
# person.name = 'John Smith'
# person.age = 70
#
# person.marshal_dump # => { :name => 'John Smith', :age => 70 }
#
def marshal_dump
@table
end
#
# Provides marshalling support for use by the Marshal library. Accepting
# a Hash of keys and values which will be used to populate the internal table
#
# require 'ostruct'
#
# event = OpenStruct.new
# hash = { 'time' => Time.now, 'title' => 'Birthday Party' }
# event.marshal_load(hash)
# event.title # => 'Birthday Party'
#
def marshal_load(x)
@table = x
@table.each_key{|key| new_ostruct_member(key)}
end
#
# #modifiable is used internally to check if the OpenStruct is able to be
# modified before granting access to the internal Hash table to be modified.
#
def modifiable
begin
@modifiable = true
rescue
raise TypeError, "can't modify frozen #{self.class}", caller(3)
end
@table
end
protected :modifiable
#
# new_ostruct_member is used internally to defined properties on the
# OpenStruct. It does this by using the metaprogramming function
# define_method for both the getter method and the setter method.
#
def new_ostruct_member(name)
name = name.to_sym
unless self.respond_to?(name)
class << self; self; end.class_eval do
define_method(name) { @table[name] }
define_method("#{name}=") { |x| modifiable[name] = x }
end
end
name
end
def method_missing(mid, *args) # :nodoc:
mname = mid.id2name
len = args.length
if mname.chomp!('=') && mid != :[]=
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 && mid != :[]
@table[mid]
else
raise NoMethodError, "undefined method `#{mid}' for #{self}", caller(1)
end
end
#
# Remove the named field from the object. Returns the value that the field
# contained if it was defined.
#
# require 'ostruct'
#
# person = OpenStruct.new('name' => 'John Smith', 'age' => 70)
#
# person.delete_field('name') # => 'John Smith'
#
def delete_field(name)
sym = name.to_sym
singleton_class.__send__(:remove_method, sym, "#{name}=")
@table.delete sym
end
InspectKey = :__inspect_key__ # :nodoc:
#
# Returns a string containing a detailed summary of the keys and values.
#
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
alias :to_s :inspect
attr_reader :table # :nodoc:
protected :table
#
# Compares this object and +other+ for equality. An OpenStruct is equal to
# +other+ when +other+ is an OpenStruct and the two object's Hash tables are
# equal.
#
def ==(other)
return false unless(other.kind_of?(OpenStruct))
return @table == other.table
end
end
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