# # = 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 # (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__ 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 TypeError, "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 raise NoMethodError, "undefined method `#{mid}' for #{self}", caller(1) 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, "#{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 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