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# frozen_string_literal: true
#
# = 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.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. <code>()[]*</code>) 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.
#
class OpenStruct
VERSION = "0.3.1"
#
# 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">
#
def initialize(hash=nil)
if hash
update_to_values!(hash)
else
@table = {}
end
end
# Duplicates an OpenStruct object's Hash table.
private def initialize_clone(orig) # :nodoc:
super # clones the singleton class for us
@table = @table.dup unless @table.frozen?
end
private def initialize_dup(orig) # :nodoc:
super
update_to_values!(@table)
end
private def update_to_values!(hash) # :nodoc:
@table = {}
hash.each_pair do |k, v|
set_ostruct_member_value!(k, v)
end
end
#
# call-seq:
# ostruct.to_h -> hash
# ostruct.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" }
#
def to_h(&block)
if block
@table.to_h(&block)
else
@table.dup
end
end
#
# :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"]]
#
def each_pair
return to_enum(__method__) { @table.size } unless block_given?
@table.each_pair{|p| yield p}
self
end
#
# Provides marshalling support for use by the Marshal library.
#
def marshal_dump # :nodoc:
@table
end
#
# Provides marshalling support for use by the Marshal library.
#
alias_method :marshal_load, :update_to_values! # :nodoc:
#
# Used internally to defined properties on the
# OpenStruct. It does this by using the metaprogramming function
# define_singleton_method for both the getter method and the setter method.
#
def new_ostruct_member!(name) # :nodoc:
unless @table.key?(name) || is_method_protected!(name)
define_singleton_method!(name) { @table[name] }
define_singleton_method!("#{name}=") {|x| @table[name] = x}
end
end
private :new_ostruct_member!
private def is_method_protected!(name) # :nodoc:
if !respond_to?(name, true)
false
elsif name.end_with?('!')
true
else
method!(name).owner < OpenStruct
end
end
def freeze
@table.freeze
super
end
private def method_missing(mid, *args) # :nodoc:
len = args.length
if mname = mid[/.*(?==\z)/m]
if len != 1
raise! ArgumentError, "wrong number of arguments (given #{len}, expected 1)", caller(1)
end
set_ostruct_member_value!(mname, args[0])
elsif len == 0
else
begin
super
rescue NoMethodError => err
err.backtrace.shift
raise!
end
end
end
#
# :call-seq:
# ostruct[name] -> object
#
# 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
#
def [](name)
@table[name.to_sym]
end
#
# :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
#
def []=(name, value)
name = name.to_sym
new_ostruct_member!(name)
@table[name] = value
end
alias_method :set_ostruct_member_value!, :[]=
private :set_ostruct_member_value!
# :call-seq:
# ostruct.dig(name, *identifiers) -> object
#
# 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}[rdoc-ref:doc/dig_methods.rdoc].
#
# 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
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
#
# 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>
#
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
InspectKey = :__inspect_key__ # :nodoc:
#
# Returns a string containing a detailed summary of the keys and values.
#
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
alias :to_s :inspect
attr_reader :table # :nodoc:
alias table! table
protected :table!
#
# 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
#
def ==(other)
return false unless other.kind_of?(OpenStruct)
@table == other.table!
end
#
# 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?.
#
def eql?(other)
return false unless other.kind_of?(OpenStruct)
@table.eql?(other.table!)
end
# Computes a hash code for this OpenStruct.
def hash # :nodoc:
@table.hash
end
#
# Provides marshalling support for use by the YAML library.
#
def encode_with(coder) # :nodoc:
@table.each_pair do |key, value|
coder[key.to_s] = value
end
if @table.size == 1 && @table.key?(:table) # support for legacy format
# in the very unlikely case of a single entry called 'table'
coder['legacy_support!'] = true # add a bogus second entry
end
end
#
# Provides marshalling support for use by the YAML library.
#
def init_with(coder) # :nodoc:
h = coder.map
if h.size == 1 # support for legacy format
key, val = h.first
if key == 'table'
h = val
end
end
update_to_values!(h)
end
# Make all public methods (builtin or our own) accessible with `!`:
instance_methods.each do |method|
new_name = "#{method}!"
alias_method new_name, method
end
# Other builtin private methods we use:
alias_method :raise!, :raise
private :raise!
end
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