Class: OpenStruct
Relationships & Source Files | |
Inherits: | Object |
Defined in: | lib/ostruct.rb |
Overview
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
= OpenStruct.new(:queued? => true)
.queued? # => true
.send("queued?=", false)
.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.
Class Method Summary
- .allocate
-
.new(hash = nil) ⇒ OpenStruct
constructor
Creates a new
OpenStruct
object.
Instance Method Summary
-
#==(other)
Compares this object and
other
for equality. -
#[](name) ⇒ Object
Returns the value of an attribute.
-
#[]=(name, obj) ⇒ Object
Sets the value of an attribute.
-
#delete_field(name)
Removes the named field from the object.
-
#dig(name, ...) ⇒ Object
Extracts the nested value specified by the sequence of
name
objects by callingdig
at each step, returningnil
if any intermediate step isnil
. -
#each_pair {|name, value| ... } ⇒ ostruct
Yields all attributes (as symbols) along with the corresponding values or returns an enumerator if no block is given.
-
#eql?(other) ⇒ Boolean
Compares this object and
other
for equality. - #freeze
-
#hash
Computes a hash code for this
OpenStruct
. -
#inspect
(also: #to_s)
Returns a string containing a detailed summary of the keys and values.
-
#marshal_dump
Provides marshalling support for use by the Marshal library.
-
#marshal_load(x)
Provides marshalling support for use by the Marshal library.
-
#to_h
Converts the
OpenStruct
to a hash with keys representing each attribute (as symbols) and their corresponding values. -
#to_s
Alias for #inspect.
-
#modifiable
protected
Used internally to check if the
OpenStruct
is able to be modified before granting access to the internal Hash table to be modified. -
#new_ostruct_member(name)
protected
Used internally to defined properties on the
OpenStruct
.
Constructor Details
.new(hash = nil) ⇒ 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", :capital => "Canberra" }
data = OpenStruct.new(hash)
data # => #<OpenStruct country="Australia", capital="Canberra">
Class Method Details
.allocate
[ GitHub ]# File 'lib/ostruct.rb', line 78
def allocate (x = super).instance_variable_set(:@table, {}) x end
Instance Method Details
#==(other)
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 345
def ==(other) return false unless other.kind_of?(OpenStruct) @table == other.table end
#[](name) ⇒ Object
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 226
def [](name) @table[name.to_sym] end
#[]=(name, obj) ⇒ Object
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 'lib/ostruct.rb', line 241
def []=(name, value) modifiable[new_ostruct_member(name)] = value end
#delete_field(name)
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 290
def delete_field(name) sym = name.to_sym begin singleton_class.__send__(:remove_method, sym, "#{sym}=") rescue NameError end @table.delete(sym) do raise NameError.new("no field `#{sym}' in #{self}", sym) end end
#dig(name, ...) ⇒ Object
Extracts the nested value specified by the sequence of name
objects by calling dig
at each step, returning nil
if any intermediate step is nil
.
require "ostruct"
address = OpenStruct.new("city" => "Anytown NC", "zip" => 12345)
person = OpenStruct.new("name" => "John Smith", "address" => address)
person.dig(:address, "zip") # => 12345
person.dig(:business_address, "zip") # => nil
data = OpenStruct.new(:array => [1, [2, 3]])
data.dig(:array, 1, 0) # => 2
data.dig(:array, 0, 0) # TypeError: Integer does not have #dig method
# File 'lib/ostruct.rb', line 265
def dig(name, *names) begin name = name.to_sym rescue NoMethodError raise TypeError, "#{name} is not a symbol nor a string" end @table.dig(name, *names) end
#each_pair {|name, value| ... } ⇒ ostruct
#each_pair ⇒ Enumerator
ostruct
#each_pair ⇒ Enumerator
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 138
def each_pair return to_enum(__method__) { @table.size } unless block_given? @table.each_pair{|p| yield p} self end
#eql?(other) ⇒ Boolean
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 355
def eql?(other) return false unless other.kind_of?(OpenStruct) @table.eql?(other.table) end
#freeze
[ GitHub ]# File 'lib/ostruct.rb', line 187
def freeze @table.each_key {|key| new_ostruct_member(key)} super end
#hash
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 365
def hash @table.hash end
#inspect Also known as: #to_s
Returns a string containing a detailed summary of the keys and values.
# File 'lib/ostruct.rb', line 306
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
#marshal_dump
Provides marshalling support for use by the Marshal library.
# File 'lib/ostruct.rb', line 147
def marshal_dump @table end
#marshal_load(x)
Provides marshalling support for use by the Marshal library.
# File 'lib/ostruct.rb', line 154
def marshal_load(x) @table = x end
#modifiable (protected)
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 162
def modifiable begin @modifiable = true rescue raise RuntimeError, "can't modify frozen #{self.class}", caller(3) end @table end
#new_ostruct_member(name) (protected)
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 177
def new_ostruct_member(name) name = name.to_sym unless singleton_class.method_defined?(name) define_singleton_method(name) { @table[name] } define_singleton_method("#{name}=") { |x| modifiable[name] = x } end name end
#to_h
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 'lib/ostruct.rb', line 122
def to_h @table.dup end
#to_s
Alias for #inspect.
# File 'lib/ostruct.rb', line 327
alias :to_s :inspect