Hi All
I''m trying to add an instance variable and a method to a object
The CODE:
#! /usr/bin/ruby
class Xyz
def initialize
p "initializing"
end
end
my_inst = Xyz.new
class <<my_inst
@new_var = "Hello world"
def get_new_var
p "instance method"
@new_var
end
end
p my_inst.get_new_var
# ========
prints:
instance method
nil
Any suggestions why the variable is ''nil'' ??
Thnx a lot
LuCa
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@new_var is a Class attribute only accessible in class methods. check this out: http://ghouston.blogspot.com/2006/06/ruby-class-variables-attributes-and.html On Jul 17, 11:04 am, Luca Scaljery <rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org> wrote:> Hi All > > I''m trying to add an instance variable and a method to a object > The CODE: > > #! /usr/bin/ruby > > class Xyz > def initialize > p "initializing" > end > end > > my_inst = Xyz.new > > class <<my_inst > @new_var = "Hello world" > > def get_new_var > p "instance method" > @new_var > end > end > > p my_inst.get_new_var > # ========> > prints: > instance method > nil > > Any suggestions why the variable is ''nil'' ?? > > Thnx a lot > LuCa > -- > Posted viahttp://www.ruby-forum.com/.--~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
I thought I opened the object so I could add instance variables to it, but I guess this should be done like my_inst.instance_variable_set(...) or can this be done like I''m trying ? -- Posted via http://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
Hi -- On Sat, 19 Jul 2008, Luca Scaljery wrote:> > I thought I opened the object so I could add instance variables to it, > but I guess this should be done like > > my_inst.instance_variable_set(...) > > or can this be done like I''m trying ?There''s a very simple rule: every time you see this: @var you are seeing an instance variable that belongs to ''self'' -- that is, whatever ''self'' happens to be at the time. Your example looks like this: class C end c = C.new class << c @x = 1 end If you check for self at that point in execution, you''ll find that self is the class you''ve just opened up -- namely, the singleton class of the object c: class << c p self # #<Class:#<C:0x7aeb8>> end So the instance variable defined at that point belongs to the class. It''s not specific to singleton classes; it''s about self. class C @x = 1 # belongs to the class object C def instance_x @x # belongs to whatever instance of C is ''self'' end end David -- Rails training from David A. Black and Ruby Power and Light: Intro to Ruby on Rails July 21-24 Edison, NJ Advancing With Rails August 18-21 Edison, NJ See http://www.rubypal.com for details and updates! --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
thnx, but how would I access the @x variable which belongs to the class object C ? -- Posted via http://www.ruby-forum.com/. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
Hi -- On Sat, 19 Jul 2008, Luca Scaljery wrote:> > thnx, but how would I access the @x variable which belongs to the class > object C ?Like any object, C can expose its instance variable through accessor methods: class << C attr_accessor :x end C.x = 1 # etc. You can also use instance_eval or instance_variable_get, but those are "impolite" ways of making an object show you its data. (Useful, but impolite :-) David -- Rails training from David A. Black and Ruby Power and Light: Intro to Ruby on Rails July 21-24 Edison, NJ Advancing With Rails August 18-21 Edison, NJ See http://www.rubypal.com for details and updates! --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
my examples uses an object not the class, so if I would do
obj = Xyz.new
class << obj
attr_accessor :x
end
how would I assign a value to x and how would I retrieve it ?
thnx a lot
--
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Hi -- On Sun, 20 Jul 2008, Luca Scaljery wrote:> > my examples uses an object not the class, so if I would do > > obj = Xyz.new > > class << obj > attr_accessor :x > end > > how would I assign a value to x and how would I retrieve it ?obj.x = 1 puts obj.x David -- Rails training from David A. Black and Ruby Power and Light: Intro to Ruby on Rails July 21-24 Edison, NJ Advancing With Rails August 18-21 Edison, NJ See http://www.rubypal.com for details and updates! --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---