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.
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
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
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
I thought they where attr_accessor method.
Thank you for clearing things up for me.
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