mirror of
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440 lines
13 KiB
Ruby
440 lines
13 KiB
Ruby
# frozen_string_literal: true
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#
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# = ostruct.rb: OpenStruct implementation
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#
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# Author:: Yukihiro Matsumoto
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# Documentation:: Gavin Sinclair
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#
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# OpenStruct allows the creation of data objects with arbitrary attributes.
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# See OpenStruct for an example.
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#
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#
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# An OpenStruct is a data structure, similar to a Hash, that allows the
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# definition of arbitrary attributes with their accompanying values. This is
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# accomplished by using Ruby's metaprogramming to define methods on the class
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# itself.
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#
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# == Examples
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#
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# require "ostruct"
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#
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# person = OpenStruct.new
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# person.name = "John Smith"
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# person.age = 70
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#
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# person.name # => "John Smith"
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# person.age # => 70
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# person.address # => nil
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#
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# An OpenStruct employs a Hash internally to store the attributes and values
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# and can even be initialized with one:
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#
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# australia = OpenStruct.new(:country => "Australia", :capital => "Canberra")
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# # => #<OpenStruct country="Australia", capital="Canberra">
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#
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# Hash keys with spaces or characters that could normally not be used for
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# method calls (e.g. <code>()[]*</code>) will not be immediately available
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# on the OpenStruct object as a method for retrieval or assignment, but can
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# still be reached through the Object#send method or using [].
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#
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# measurements = OpenStruct.new("length (in inches)" => 24)
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# measurements[:"length (in inches)"] # => 24
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# measurements.send("length (in inches)") # => 24
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#
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# message = OpenStruct.new(:queued? => true)
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# message.queued? # => true
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# message.send("queued?=", false)
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# message.queued? # => false
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#
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# Removing the presence of an attribute requires the execution of the
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# delete_field method as setting the property value to +nil+ will not
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# remove the attribute.
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#
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# first_pet = OpenStruct.new(:name => "Rowdy", :owner => "John Smith")
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# second_pet = OpenStruct.new(:name => "Rowdy")
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#
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# first_pet.owner = nil
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# first_pet # => #<OpenStruct name="Rowdy", owner=nil>
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# first_pet == second_pet # => false
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#
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# first_pet.delete_field(:owner)
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# first_pet # => #<OpenStruct name="Rowdy">
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# first_pet == second_pet # => true
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#
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# Ractor compatibility: A frozen OpenStruct with shareable values is itself shareable.
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#
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# == Caveats
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#
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# An OpenStruct utilizes Ruby's method lookup structure to find and define the
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# necessary methods for properties. This is accomplished through the methods
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# method_missing and define_singleton_method.
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#
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# This should be a consideration if there is a concern about the performance of
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# the objects that are created, as there is much more overhead in the setting
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# of these properties compared to using a Hash or a Struct.
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# Creating an open struct from a small Hash and accessing a few of the
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# entries can be 200 times slower than accessing the hash directly.
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#
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# This is a potential security issue; building OpenStruct from untrusted user data
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# (e.g. JSON web request) may be susceptible to a "symbol denial of service" attack
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# since the keys create methods and names of methods are never garbage collected.
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#
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# This may also be the source of incompatibilities between Ruby versions:
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#
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# o = OpenStruct.new
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# o.then # => nil in Ruby < 2.6, enumerator for Ruby >= 2.6
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#
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# Builtin methods may be overwritten this way, which may be a source of bugs
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# or security issues:
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#
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# o = OpenStruct.new
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# o.methods # => [:to_h, :marshal_load, :marshal_dump, :each_pair, ...
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# o.methods = [:foo, :bar]
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# o.methods # => [:foo, :bar]
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#
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# To help remedy clashes, OpenStruct uses only protected/private methods ending with `!`
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# and defines aliases for builtin public methods by adding a `!`:
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#
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# o = OpenStruct.new(make: 'Bentley', class: :luxury)
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# o.class # => :luxury
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# o.class! # => OpenStruct
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#
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# It is recommended (but not enforced) to not use fields ending in `!`;
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# Note that a subclass' methods may not be overwritten, nor can OpenStruct's own methods
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# ending with `!`.
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#
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# For all these reasons, consider not using OpenStruct at all.
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#
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class OpenStruct
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VERSION = "0.3.2"
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#
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# Creates a new OpenStruct object. By default, the resulting OpenStruct
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# object will have no attributes.
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#
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# The optional +hash+, if given, will generate attributes and values
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# (can be a Hash, an OpenStruct or a Struct).
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# For example:
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#
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# require "ostruct"
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# hash = { "country" => "Australia", :capital => "Canberra" }
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# data = OpenStruct.new(hash)
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#
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# data # => #<OpenStruct country="Australia", capital="Canberra">
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#
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def initialize(hash=nil)
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if hash
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update_to_values!(hash)
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else
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@table = {}
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end
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end
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# Duplicates an OpenStruct object's Hash table.
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private def initialize_clone(orig) # :nodoc:
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super # clones the singleton class for us
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@table = @table.dup unless @table.frozen?
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end
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private def initialize_dup(orig) # :nodoc:
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super
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update_to_values!(@table)
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end
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private def update_to_values!(hash) # :nodoc:
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@table = {}
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hash.each_pair do |k, v|
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set_ostruct_member_value!(k, v)
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end
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end
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#
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# call-seq:
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# ostruct.to_h -> hash
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# ostruct.to_h {|name, value| block } -> hash
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#
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# Converts the OpenStruct to a hash with keys representing
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# each attribute (as symbols) and their corresponding values.
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#
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# If a block is given, the results of the block on each pair of
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# the receiver will be used as pairs.
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#
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# require "ostruct"
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# data = OpenStruct.new("country" => "Australia", :capital => "Canberra")
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# data.to_h # => {:country => "Australia", :capital => "Canberra" }
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# data.to_h {|name, value| [name.to_s, value.upcase] }
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# # => {"country" => "AUSTRALIA", "capital" => "CANBERRA" }
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#
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def to_h(&block)
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if block
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@table.to_h(&block)
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else
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@table.dup
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end
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end
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#
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# :call-seq:
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# ostruct.each_pair {|name, value| block } -> ostruct
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# ostruct.each_pair -> Enumerator
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#
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# Yields all attributes (as symbols) along with the corresponding values
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# or returns an enumerator if no block is given.
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#
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# require "ostruct"
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# data = OpenStruct.new("country" => "Australia", :capital => "Canberra")
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# data.each_pair.to_a # => [[:country, "Australia"], [:capital, "Canberra"]]
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#
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def each_pair
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return to_enum(__method__) { @table.size } unless block_given?
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@table.each_pair{|p| yield p}
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self
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end
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#
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# Provides marshalling support for use by the Marshal library.
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#
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def marshal_dump # :nodoc:
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@table
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end
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#
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# Provides marshalling support for use by the Marshal library.
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#
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alias_method :marshal_load, :update_to_values! # :nodoc:
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#
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# Used internally to defined properties on the
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# OpenStruct. It does this by using the metaprogramming function
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# define_singleton_method for both the getter method and the setter method.
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#
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def new_ostruct_member!(name) # :nodoc:
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unless @table.key?(name) || is_method_protected!(name)
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define_singleton_method!(name) { @table[name] }
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define_singleton_method!("#{name}=") {|x| @table[name] = x}
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end
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end
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private :new_ostruct_member!
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private def is_method_protected!(name) # :nodoc:
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if !respond_to?(name, true)
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false
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elsif name.end_with?('!')
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true
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else
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owner = method!(name).owner
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if owner.class == ::Class
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owner < ::OpenStruct
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else
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self.class.ancestors.any? do |mod|
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return false if mod == ::OpenStruct
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mod == owner
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end
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end
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end
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end
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def freeze
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@table.freeze
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super
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end
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private def method_missing(mid, *args) # :nodoc:
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len = args.length
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if mname = mid[/.*(?==\z)/m]
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if len != 1
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raise! ArgumentError, "wrong number of arguments (given #{len}, expected 1)", caller(1)
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end
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set_ostruct_member_value!(mname, args[0])
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elsif len == 0
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@table[mid]
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else
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begin
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super
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rescue NoMethodError => err
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err.backtrace.shift
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raise!
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end
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end
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end
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#
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# :call-seq:
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# ostruct[name] -> object
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#
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# Returns the value of an attribute, or `nil` if there is no such attribute.
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#
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# require "ostruct"
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# person = OpenStruct.new("name" => "John Smith", "age" => 70)
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# person[:age] # => 70, same as person.age
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#
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def [](name)
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@table[name.to_sym]
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end
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#
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# :call-seq:
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# ostruct[name] = obj -> obj
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#
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# Sets the value of an attribute.
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#
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# require "ostruct"
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# person = OpenStruct.new("name" => "John Smith", "age" => 70)
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# person[:age] = 42 # equivalent to person.age = 42
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# person.age # => 42
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#
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def []=(name, value)
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name = name.to_sym
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new_ostruct_member!(name)
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@table[name] = value
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end
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alias_method :set_ostruct_member_value!, :[]=
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private :set_ostruct_member_value!
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# :call-seq:
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# ostruct.dig(name, *identifiers) -> object
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#
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# Finds and returns the object in nested objects
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# that is specified by +name+ and +identifiers+.
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# The nested objects may be instances of various classes.
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# See {Dig Methods}[rdoc-ref:doc/dig_methods.rdoc].
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#
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# Examples:
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# require "ostruct"
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# address = OpenStruct.new("city" => "Anytown NC", "zip" => 12345)
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# person = OpenStruct.new("name" => "John Smith", "address" => address)
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# person.dig(:address, "zip") # => 12345
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# person.dig(:business_address, "zip") # => nil
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def dig(name, *names)
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begin
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name = name.to_sym
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rescue NoMethodError
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raise! TypeError, "#{name} is not a symbol nor a string"
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end
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@table.dig(name, *names)
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end
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#
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# Removes the named field from the object. Returns the value that the field
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# contained if it was defined.
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#
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# require "ostruct"
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#
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# person = OpenStruct.new(name: "John", age: 70, pension: 300)
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#
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# person.delete_field!("age") # => 70
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# person # => #<OpenStruct name="John", pension=300>
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#
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# Setting the value to +nil+ will not remove the attribute:
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#
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# person.pension = nil
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# person # => #<OpenStruct name="John", pension=nil>
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#
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def delete_field(name)
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sym = name.to_sym
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begin
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singleton_class.remove_method(sym, "#{sym}=")
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rescue NameError
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end
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@table.delete(sym) do
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raise! NameError.new("no field `#{sym}' in #{self}", sym)
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end
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end
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InspectKey = :__inspect_key__ # :nodoc:
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#
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# Returns a string containing a detailed summary of the keys and values.
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#
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def inspect
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ids = (Thread.current[InspectKey] ||= [])
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if ids.include?(object_id)
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detail = ' ...'
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else
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ids << object_id
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begin
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detail = @table.map do |key, value|
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" #{key}=#{value.inspect}"
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end.join(',')
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ensure
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ids.pop
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end
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end
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['#<', self.class!, detail, '>'].join
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end
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alias :to_s :inspect
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attr_reader :table # :nodoc:
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alias table! table
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protected :table!
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#
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# Compares this object and +other+ for equality. An OpenStruct is equal to
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# +other+ when +other+ is an OpenStruct and the two objects' Hash tables are
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# equal.
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#
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# require "ostruct"
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# first_pet = OpenStruct.new("name" => "Rowdy")
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# second_pet = OpenStruct.new(:name => "Rowdy")
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# third_pet = OpenStruct.new("name" => "Rowdy", :age => nil)
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#
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# first_pet == second_pet # => true
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# first_pet == third_pet # => false
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#
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def ==(other)
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return false unless other.kind_of?(OpenStruct)
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@table == other.table!
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end
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#
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# Compares this object and +other+ for equality. An OpenStruct is eql? to
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# +other+ when +other+ is an OpenStruct and the two objects' Hash tables are
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# eql?.
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#
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def eql?(other)
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return false unless other.kind_of?(OpenStruct)
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@table.eql?(other.table!)
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end
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# Computes a hash code for this OpenStruct.
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def hash # :nodoc:
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@table.hash
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end
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#
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# Provides marshalling support for use by the YAML library.
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#
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def encode_with(coder) # :nodoc:
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@table.each_pair do |key, value|
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coder[key.to_s] = value
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end
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if @table.size == 1 && @table.key?(:table) # support for legacy format
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# in the very unlikely case of a single entry called 'table'
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coder['legacy_support!'] = true # add a bogus second entry
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end
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end
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#
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# Provides marshalling support for use by the YAML library.
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#
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def init_with(coder) # :nodoc:
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h = coder.map
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if h.size == 1 # support for legacy format
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key, val = h.first
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if key == 'table'
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h = val
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end
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end
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update_to_values!(h)
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end
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# Make all public methods (builtin or our own) accessible with `!`:
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instance_methods.each do |method|
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new_name = "#{method}!"
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alias_method new_name, method
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end
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# Other builtin private methods we use:
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alias_method :raise!, :raise
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private :raise!
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end
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