Method not receiving object values

rubyonrails-talk
1

Hi everyone,

I'm having a weird issue

I have a Study model that has several fields, but to mention a few (or that ones that I'm having troubles with) are

- profesion_related - profesion_name

I have this in my controller

def create   @study = Study.new(params[:study])   respond_to do |format|     if @study.save        #code here     else        #more code here     end   end end

and in my model

class Study < AR....   #there are other attr_accessible but just wanted to show this   attr_accessible :profesion_related   attr_accessor :profesion_related

  def profesion_related=(id)     profesion_parent = Profesion.find(id)     ######below here the last attribute is the one that is empty     new_profesion = Profesion.create({m_code: profesion_parent.m_code, g_code: profesion_parent.g_code, name: self.profesion_name})   end

end

I'm getting an error there because self.profesion_name is empty, but in my log I see that it's being sent and also if I put in my create action

       @study = Study.new(params[:study] -> puts @study.to_yaml         respond_to

I can see that the object @study has every single attribute filled, but inside the profesion_related method in my model, the self.profesion_name is empty

What could be wrong with this? Hope someone can help me

Thanks in advance

2

It’s possible that the profesion_name is not set yet – you might want to consider creating the Profesion model in a before_save callback. I suspect there are some issues with how this is model, but hopeful this suggestion will get you moving foward.

Cheers, Nicholas

3

Hi everyone,

end

I'm getting an error there because self.profesion_name is empty, but in my log I see that it's being sent and also if I put in my create action

   @study = Study\.new\(params\[:study\]

-> puts @study.to_yaml respond_to

I can see that the object @study has every single attribute filled, but inside the profesion_related method in my model, the self.profesion_name is empty

What could be wrong with this? Hope someone can help

An activerecord object's initialize method basically does

attributes.each do |attr_name, value |     send("#{attr_name}=", value) end

So at some point it will call self.profession_name = and at some point it will call self.profession_related but there's no particular order that is is guaranteed to happen in (on ruby 1.9 I wouldn't be surprised if it was the order of the fields on the page)

You might want to consider building the profession either outside of new entirely or in a callback. It's also possible that how you've modelled it is making it more complicated than it has to be but it's hard to tell that from here.

Fred

4

Hi guys,

Thanks both for the reply, I know it could be done by using a callback but there are more code inside that method.

5

No, there isn’t. Callbacks are your best bet.

6

In the end I made a before_validation callback and inside that I'm using the virtual attribute, but I'm still wondering how AR order the list of attributes

I started here

but I'm not sure where should I go next. Hope somebody can guide me

Thanks

Javier

7

IMHO AR lists the attributes as it receives them from schema and any virtual attributes from the model. This is because attributes is a hash, and Ruby 1.9 maintains the key order in a hash.

If your code depends on the order of attributes defined, it’s definitely a smell.

8

No, there isn't. Callbacks are your best bet.

In the end I made a before_validation callback and inside that I'm using the virtual attribute, but I'm still wondering how AR order the list of attributes

I started here https://github.com/rails/rails/blob/3-2-stable/activerecord/lib/active_record/base.rb#L481 but I'm not sure where should I go next. Hope somebody can guide me

Here is a link to view the assignment of attributes in ActiveRecord code base:

9

Well, I did a before_validation callback

def bv_callback    puts self.to_yaml end

and I can see that the object has profesion_name (and every other) attribute setted

but here

def profesion_related=(id)    puts self.to_yaml end

there are only 3 attributes filled. I'm still not getting how does AR manages to fill each attribute of the object after being saved

10

Simple. First, all setter methods are called on AR, and I’m guessing profesion_related= was called the fourth, so only three attributes are filled. After all setter methods are called (which means all attributes are populated) the callbacks start, the first being the before_validation one, which shows you the entire AR object.

11

If that's the case... I'm not sure how to proceed then :frowning: I thought active record would set object attributes first, and then virtual attributes or attr_writer methods I'm doing this writer method because of this

def profesion_related=(value)    if value.to_i.to_s == value       #some code here if value is a number    else       #create a new profesion if is an string    end    #there's a select input that changes the type of the profesion_related input in my form (between a select input and a text input end

As far as I tried I can't retrieve profesion_related value in my before_validation callback cause its a virtual attribute

12

You should be able to retrieve the value in the callback. If it isn’t, you’re doing something wrong. Make sure you remove your setters. Use just the callback. If it doesn’t work, gist your code.