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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 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
# (can be a Hash, an OpenStruct or a Struct).
# 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
hash.each_pair do |k, v|
k = k.to_sym
@table[k] = 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
#
# Yields all attributes (as a symbol) along with the corresponding values
# or returns an enumerator if not block is given.
# Example:
#
# require 'ostruct'
# data = OpenStruct.new("country" => "Australia", :population => 20_000_000)
# data.each_pair.to_a # => [[:country, "Australia"], [:population, 20000000]]
#
def each_pair
return to_enum(__method__) { @table.size } unless block_given?
@table.each_pair{|p| yield p}
end
#
# Provides marshalling support for use by the Marshal library.
#
def marshal_dump
@table
end
#
# Provides marshalling support for use by the Marshal library.
#
def marshal_load(x)
@table = x
@table.each_key{|key| new_ostruct_member(key)}
end
#
# 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 RuntimeError, "can't modify frozen #{self.class}", caller(3)
end
@table
end
protected :modifiable
#
# 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)
name = name.to_sym
unless respond_to?(name)
define_singleton_method(name) { @table[name] }
define_singleton_method("#{name}=") { |x| modifiable[name] = x }
end
name
end
protected :new_ostruct_member
def method_missing(mid, *args) # :nodoc:
mname = mid.id2name
len = args.length
if mname.chomp!('=')
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
@table[mid]
else
err = NoMethodError.new "undefined method `#{mid}' for #{self}", mid, args
err.set_backtrace caller(1)
raise err
end
end
# Returns the value of a member.
#
# person = OpenStruct.new('name' => 'John Smith', 'age' => 70)
# person[:age] # => 70, same as ostruct.age
#
def [](name)
@table[name.to_sym]
end
#
# Sets the value of a member.
#
# person = OpenStruct.new('name' => 'John Smith', 'age' => 70)
# person[:age] = 42 # => equivalent to ostruct.age = 42
# person.age # => 42
#
def []=(name, value)
modifiable[new_ostruct_member(name)] = value
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, "#{sym}=")
@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 objects' Hash tables are
# equal.
#
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
# Compute a hash-code for this OpenStruct.
# Two hashes with the same content will have the same hash code
# (and will be eql?).
def hash
@table.hash
end
end
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