Can we see the singleton class as object in ruby.
On Fri, Jun 25, 2010 at 6:11 AM, Manoj K. [email protected]
wrote:
Can we see the singleton class as object in ruby.
Like this?
irb(main):001:0> o = Object.new
=> #Object:0xb743f3fc
irb(main):002:0> singleton = class << o; self; end
=> #<Class:#Object:0xb743f3fc>
irb(main):003:0> singleton
=> #<Class:#Object:0xb743f3fc>
irb(main):004:0> def o.test; “test”; end
=> nil
irb(main):008:0> singleton.instance_methods(false)
=> [“test”]
Jesus.
Hi Jesus,
Thanks for your reply.
class Sample
def in_class
‘in_class’
end
end
@sample = Sample.new
@sample.instance_eval do
def in_singleton
‘in singleton’
end
end
In @sample object, in_class method will be available in Sample class.
But in_singleton method will be available in sinlgeton class of @sample.
That singleton class will be available in memory.
But i couldn’t see that class in the form of object or some thing else.
Thanks,
Manoj
Jesús Gabriel y Galán wrote:
On Fri, Jun 25, 2010 at 6:11 AM, Manoj K. [email protected]
wrote:Can we see the singleton class as object in ruby.
Like this?
irb(main):001:0> o = Object.new
=> #Object:0xb743f3fc
irb(main):002:0> singleton = class << o; self; end
=> #<Class:#Object:0xb743f3fc>
irb(main):003:0> singleton
=> #<Class:#Object:0xb743f3fc>
irb(main):004:0> def o.test; “test”; end
=> nil
irb(main):008:0> singleton.instance_methods(false)
=> [“test”]Jesus.
As you said class << o; self; end
In Rails, there is a method called metaclass which is defined in Object
def metaclass
class << self
self
end
end
is #<Class:#Object:0xb743f3fc> the singleton class object for object
o?
On 27 June 2010 16:43, Manoj K. [email protected] wrote:
As you said class << o; self; end
In Rails, there is a method called metaclass which is defined in Object
def metaclass
class << self
self
end
end
Yes, and this method is now deprecated because of the wrong name.
The chosen name is … singleton_class
So, the answer, in Ruby 1.9 is“mystr”.singleton_class
=> #<Class:#String:0x00000100864fd8>
is #<Class:#Object:0xb743f3fc> the singleton class object for object
o?
yes.
B.D.
Benoit D. wrote:
On 27 June 2010 16:43, Manoj K. [email protected] wrote:
As you said � class << o; self; end
In Rails, there is a method called metaclass which is defined in Object
def metaclass
�class << self
� �self
�end
end
Yes, and this method is now deprecated because of the wrong name.
The chosen name is … singleton_class
So, the answer, in Ruby 1.9 is“mystr”.singleton_class
=> #<Class:#String:0x00000100864fd8>is #<Class:#Object:0xb743f3fc> the singleton class object for object
o?
yes.B.D.
Thanks Benoit.
If i try,
singleton.instance_methods(false), it is returning [“test”].
But, ‘test’ method is not available in singleton.methods. But it is
available in singleton.instance_methods.
Why it is like this? Any special reason for this?
Thanks,
Manoj
On Mon, Jun 28, 2010 at 7:01 AM, Manoj K. [email protected]
wrote:
end
B.D.
available in singleton.instance_methods.Why it is like this? Any special reason for this?
Because methods returns the list of methods that are accessible for
the object. In the case of the singleton class, it’s the instance of
the class (the object) for which you call the method “test”. It’s the
same thing as with regular classes:
irb(main):001:0> class A
irb(main):002:1> def test
irb(main):003:2> “test”
irb(main):004:2> end
irb(main):005:1> end
=> nil
irb(main):006:0> A.methods.grep(/test/)
=> []
irb(main):007:0> A.instance_methods.grep(/test/)
=> [“test”]
irb(main):008:0> a = A.new
=> #<A:0xb74d2274>
irb(main):009:0> a.methods.grep(/test/)
=> [“test”]
Jesus.
Jesús Gabriel y Galán wrote:
On Mon, Jun 28, 2010 at 7:01 AM, Manoj K. [email protected]
wrote:end
B.D.
available in singleton.instance_methods.Why it is like this? Any special reason for this?
Because methods returns the list of methods that are accessible for
the object. In the case of the singleton class, it’s the instance of
the class (the object) for which you call the method “test”. It’s the
same thing as with regular classes:irb(main):001:0> class A
irb(main):002:1> def test
irb(main):003:2> “test”
irb(main):004:2> end
irb(main):005:1> end
=> nil
irb(main):006:0> A.methods.grep(/test/)
=> []
irb(main):007:0> A.instance_methods.grep(/test/)
=> [“test”]
irb(main):008:0> a = A.new
=> #<A:0xb74d2274>
irb(main):009:0> a.methods.grep(/test/)
=> [“test”]Jesus.
Thanks Jesus,
manoj