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.
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
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.
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>
# File lib/ostruct.rb, line 87
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 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.
# File lib/ostruct.rb, line 265 def ==(other) return false unless other.kind_of?(OpenStruct) @table == other.table end
Returns the value of a member.
person = OpenStruct.new('name' => 'John Smith', 'age' => 70)
person[:age] # => 70, same as ostruct.age
# File lib/ostruct.rb, line 198 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
# File lib/ostruct.rb, line 209 def []=(name, value) modifiable[new_ostruct_member(name)] = value end
Returns a hash, that will be turned into a JSON object and represent this object.
# File ext/json/lib/json/add/ostruct.rb, line 16
def as_json(*)
klass = self.class.name
klass.to_s.empty? and raise JSON::JSONError, "Only named structs are supported!"
{
JSON.create_id => klass,
't' => table,
}
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'
# File lib/ostruct.rb, line 223
def delete_field(name)
sym = name.to_sym
singleton_class.__send__(:remove_method, sym, "#{sym}=")
@table.delete sym
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]]
# File lib/ostruct.rb, line 127
def each_pair
return to_enum(__method__) { @table.size } unless block_given?
@table.each_pair{|p| yield p}
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?.
# File lib/ostruct.rb, line 275 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?).
# File lib/ostruct.rb, line 283 def hash @table.hash end
Duplicate an OpenStruct object members.
# File lib/ostruct.rb, line 99
def initialize_copy(orig)
super
@table = @table.dup
@table.each_key{|key| new_ostruct_member(key)}
end Returns a string containing a detailed summary of the keys and values.
# File lib/ostruct.rb, line 234
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 Provides marshalling support for use by the Marshal library.
# File lib/ostruct.rb, line 135 def marshal_dump @table end
Provides marshalling support for use by the Marshal library.
# File lib/ostruct.rb, line 142
def marshal_load(x)
@table = x
@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 }
# File lib/ostruct.rb, line 114 def to_h @table.dup end
Stores class name (OpenStruct) with this struct's values v as a JSON string.
# File ext/json/lib/json/add/ostruct.rb, line 27 def to_json(*args) as_json.to_json(*args) end
Used internally to check if the OpenStruct is able to be modified before granting access to the internal Hash table to be modified.
# File lib/ostruct.rb, line 151
def modifiable
begin
@modifiable = true
rescue
raise RuntimeError, "can't modify frozen #{self.class}", caller(3)
end
@table
end 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.
# File lib/ostruct.rb, line 166
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
Ruby Core © 1993–2016 Yukihiro Matsumoto
Licensed under the Ruby License.
Ruby Standard Library © contributors
Licensed under their own licenses.