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class OpenStruct
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. ()[]*
) 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.
measurements = OpenStruct.new("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
Implementation
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.
Public Class Methods
# File lib/ostruct.rb, line 89
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
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">
Public Instance Methods
# File lib/ostruct.rb, line 293
def ==(other)
return false unless other.kind_of?(OpenStruct)
@table == other.table
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.
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
# File lib/ostruct.rb, line 208
def [](name)
@table[name.to_sym]
end
Returns the value of an attribute.
require "ostruct"
person = OpenStruct.new("name" => "John Smith", "age" => 70)
person[:age] # => 70, same as person.age
# File lib/ostruct.rb, line 223
def []=(name, value)
modifiable[new_ostruct_member(name)] = value
end
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
# 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
Returns a hash, that will be turned into a JSON object and represent this object.
# File lib/ostruct.rb, line 243
def delete_field(name)
sym = name.to_sym
singleton_class.__send__(:remove_method, sym, "#{sym}=")
@table.delete sym
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>
# File lib/ostruct.rb, line 131
def each_pair
return to_enum(__method__) { @table.size } unless block_given?
@table.each_pair{|p| yield p}
self
end
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"]]
# File lib/ostruct.rb, line 303
def eql?(other)
return false unless other.kind_of?(OpenStruct)
@table.eql?(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?.
# File lib/ostruct.rb, line 313
def hash
@table.hash
end
Computes a hash code for this OpenStruct. Two OpenStruct objects with the same content will have the same hash code (and will compare using eql?).
See also Object#hash.
# File lib/ostruct.rb, line 254
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
Returns a string containing a detailed summary of the keys and values.
# File lib/ostruct.rb, line 140
def marshal_dump
@table
end
Provides marshalling support for use by the Marshal library.
# File lib/ostruct.rb, line 147
def marshal_load(x)
@table = x
@table.each_key{|key| new_ostruct_member(key)}
end
Provides marshalling support for use by the Marshal library.
# File lib/ostruct.rb, line 115
def to_h
@table.dup
end
Converts the OpenStruct to a hash with keys representing each attribute (as symbols) and their corresponding values.
require "ostruct"
data = OpenStruct.new("country" => "Australia", :capital => "Canberra")
data.to_h # => {:country => "Australia", :capital => "Canberra" }
# File ext/json/lib/json/add/ostruct.rb, line 27
def to_json(*args)
as_json.to_json(*args)
end
Stores class name (OpenStruct) with this struct's values v
as a JSON string.
Protected Instance Methods
# File lib/ostruct.rb, line 156
def modifiable
begin
@modifiable = true
rescue
raise RuntimeError, "can't modify frozen #{self.class}", caller(3)
end
@table
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 171
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
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.
Ruby Core © 1993–2017 Yukihiro Matsumoto
Licensed under the Ruby License.
Ruby Standard Library © contributors
Licensed under their own licenses.