Hi, I''d like to know why I can''t, or how can I, access
attributes like that:
class User < ActiveRecord::Base
def name
@first_name + @last_name
end
end
first_name and last_name are user attributes in the database.
Thanks in advance.
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Benjamin Iandavid Rodriguez
2012-Jan-30 20:19 UTC
Re: Why can''t I access attributes in rails model?
Have this instance variables been set anywhere in your app? If not, you wont be able to access attributes anywhere. I suggest to first find a record in the DB and set the results to and instance variable like: @var = User.find(params[:some_params]) and then you will be able to access attributes for that object @var.name + @var.lastname 2012/1/30 Rodrigo Ruiz <rodrigo.ruiz7-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>> Hi, I''d like to know why I can''t, or how can I, access attributes like > that: > > class User < ActiveRecord::Base > def name > @first_name + @last_name > end > end > > first_name and last_name are user attributes in the database. > > Thanks in advance. > > -- > 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-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org > To unsubscribe from this group, send email to > rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org > For more options, visit this group at > http://groups.google.com/group/rubyonrails-talk?hl=en. >-- 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-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Peter Vandenabeele
2012-Jan-30 20:25 UTC
Re: Why can''t I access attributes in rails model?
On Mon, Jan 30, 2012 at 9:09 PM, Rodrigo Ruiz <rodrigo.ruiz7-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>wrote:> Hi, I''d like to know why I can''t, or how can I, access attributes like > that: > > class User < ActiveRecord::Base > def name > @first_name + @last_name > end > end > > first_name and last_name are user attributes in the database. >ActiveRecord dynamically defines "accessor methods" on the user instance. That user instance is accessible as ''self'' inside the user instance, so you could do class User < ActiveRecord::Base def name self.first_name + self.last_name end end But, in Ruby, when using a _read_ accessor, you could also write it without the explicit ''self''. class User < ActiveRecord::Base def name first_name + last_name # same as self.first_name + self.last_name # if there is no first_name, last_name local variable # defined in the scope end end For _write_ accessors, you _must_ put the self in front, that is: self.full_name = "#{first_name} #{last_name}" And the @first_name you asked about, that is an "instance variable". Read one of the many Ruby tutorials or books to understand this better. HTH, Peter -- 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-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Thank you, but I knew that, I did that (use self to do what I want) before I asked the question. I''d just like to know why can''t I use @first_name instead of self.first_name, to me it seems like the same thing inside the model. On Mon, Jan 30, 2012 at 6:25 PM, Peter Vandenabeele <peter-jNuWw7i2w7syMbTcgqFhxg@public.gmane.org>wrote:> On Mon, Jan 30, 2012 at 9:09 PM, Rodrigo Ruiz <rodrigo.ruiz7-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>wrote: > >> Hi, I''d like to know why I can''t, or how can I, access attributes like >> that: >> >> class User < ActiveRecord::Base >> def name >> @first_name + @last_name >> end >> end >> >> first_name and last_name are user attributes in the database. >> > > ActiveRecord dynamically defines "accessor methods" on the > user instance. > > That user instance is accessible as ''self'' inside the user instance, > so you could do > > class User < ActiveRecord::Base > def name > self.first_name + self.last_name > end > end > > But, in Ruby, when using a _read_ accessor, you could also write it > without the explicit ''self''. > > class User < ActiveRecord::Base > def name > first_name + last_name > # same as self.first_name + self.last_name > # if there is no first_name, last_name local variable > # defined in the scope > end > end > > For _write_ accessors, you _must_ put the self in front, that is: > > self.full_name = "#{first_name} #{last_name}" > > And the @first_name you asked about, that is an "instance variable". > > Read one of the many Ruby tutorials or books to understand this better. > > HTH, > > Peter > > -- > 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-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org > To unsubscribe from this group, send email to > rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org > For more options, visit this group at > http://groups.google.com/group/rubyonrails-talk?hl=en. >-- 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-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Peter Vandenabeele
2012-Jan-30 21:07 UTC
Re: Why can''t I access attributes in rails model?
On Mon, Jan 30, 2012 at 9:59 PM, Rodrigo Ruiz <rodrigo.ruiz7-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>wrote:> Thank you, but I knew that, I did that (use self to do what I want) before > I asked the question. > > I''d just like to know why can''t I use @first_name instead of > self.first_name, to me it seems like the same thing inside the model. >They are not: @first_name is an "instance variable". You could set it like this: @first_name = user.first_name but it is not automatically set, and it is also not typically used like that. A more typical use would be: @user = User.find(params[:id]) and then you can use @user in the controller, but also in the views, due to the set-up of Rails. self.first_name is a method that is dynamically provided by ActiveRecord , based on the available columns for the table "users" in the database. HTH, Peter -- 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-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
I thought they where attr_accessor method. Thank you for clearing things up for me. On Monday, January 30, 2012, Peter Vandenabeele <peter-jNuWw7i2w7syMbTcgqFhxg@public.gmane.org> wrote:> On Mon, Jan 30, 2012 at 9:59 PM, Rodrigo Ruiz <rodrigo.ruiz7-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>wrote:>> >> Thank you, but I knew that, I did that (use self to do what I want)before I asked the question.>> I''d just like to know why can''t I use @first_name instead ofself.first_name, to me it seems like the same thing inside the model.> > They are not: > @first_name is an "instance variable". You could set it like this: > @first_name = user.first_name > but it is not automatically set, and it is also not typically used likethat.> A more typical use would be: > @user = User.find(params[:id]) > and then you can use @user in the controller, but also in the views, > due to the set-up of Rails. > self.first_name is a method that is dynamically provided by > ActiveRecord , based on the available columns for the table > "users" in the database. > HTH, > Peter > > -- > 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-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org > To unsubscribe from this group, send email torubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org> For more options, visit this group athttp://groups.google.com/group/rubyonrails-talk?hl=en.>-- 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-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
On Jan 31, 2:29 am, Rodrigo Ruiz <rodrigo.ru...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> I thought they where attr_accessor method. > > Thank you for clearing things up for me.To add a little more info, the attribute values are stored in the @attributes / @attributes_cache hashes Fred> > On Monday, January 30, 2012, Peter Vandenabeele <pe...-jNuWw7i2w7syMbTcgqFhxg@public.gmane.org> > wrote:> On Mon, Jan 30, 2012 at 9:59 PM, Rodrigo Ruiz <rodrigo.ru...@gmail.com> > wrote: > > >> Thank you, but I knew that, I did that (use self to do what I want) > > before I asked the question.>> I''d just like to know why can''t I use @first_name instead of > > self.first_name, to me it seems like the same thing inside the model. > > > > > > > > > > > They are not: > > @first_name is an "instance variable". You could set it like this: > > @first_name = user.first_name > > but it is not automatically set, and it is also not typically used like > that. > > A more typical use would be: > > @user = User.find(params[:id]) > > and then you can use @user in the controller, but also in the views, > > due to the set-up of Rails. > > self.first_name is a method that is dynamically provided by > > ActiveRecord , based on the available columns for the table > > "users" in the database. > > HTH, > > Peter > > > -- > > 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-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org > > To unsubscribe from this group, send email to > > rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org> For more options, visit this group at > > http://groups.google.com/group/rubyonrails-talk?hl=en. > > > > > > > >-- 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-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@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.