thr3ads.net - Rails - problem with has_many :through association [Oct 2007]

If this information is useful, please help other people find it:
Share via:

chirag

2007-Oct-03 01:50 UTC

problem with has_many :through association

I have the following models

   1. class Caregiver < ActiveRecord::Base
   2.   has_many :call_orders
   3.   has_many :users, :through => :call_orders
   4. end
   5.
   6. class User < ActiveRecord::Base
   7.   has_many :call_orders, :order => :position
   8.   has_many :caregivers, :through => :call_orders
   9. end
  10.
  11. class CallOrder < ActiveRecord::Base
  12.   belongs_to :user
  13.   belongs_to :caregiver
  14.   acts_as_list :scope => :user
  15. end


When I run the following commands, I get an error:

   1. @call_list = User.find(params[:id])
   2. @call_list.call_orders.each do |call_order|
   3. puts call_order.caregiver.first_name


This is the error:

   You have a nil object when you didn''t expect it!
   The error occurred while evaluating nil.first_name


--~--~---------~--~----~------------~-------~--~----~
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
-~----------~----~----~----~------~----~------~--~---

Michael Wang

2007-Oct-04 05:03 UTC

head link

Re: problem with has_many :through association

chirag wrote:> I have the following models
> 
>    1. class Caregiver < ActiveRecord::Base
>    2.   has_many :call_orders
>    3.   has_many :users, :through => :call_orders
>    4. end
>    5.
>    6. class User < ActiveRecord::Base
>    7.   has_many :call_orders, :order => :position
>    8.   has_many :caregivers, :through => :call_orders
>    9. end
>   10.
>   11. class CallOrder < ActiveRecord::Base
>   12.   belongs_to :user
>   13.   belongs_to :caregiver
>   14.   acts_as_list :scope => :user
>   15. end
> 
> 
> When I run the following commands, I get an error:
> 
>    1. @call_list = User.find(params[:id])
>    2. @call_list.call_orders.each do |call_order|
>    3. puts call_order.caregiver.first_name
> 
> 
> This is the error:
> 
>    You have a nil object when you didn''t expect it!
>    The error occurred while evaluating nil.first_name
What do your tables/migrations look like?


-- 
Michael Wang

--~--~---------~--~----~------------~-------~--~----~
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
-~----------~----~----~----~------~----~------~--~---

chirag

2007-Oct-04 05:12 UTC

head link

Re: problem with has_many :through association

class CreateCaregivers < ActiveRecord::Migration
  def self.up
    create_table :caregivers do |t|
      t.column :first_name, :string
      t.column :last_name, :string
      t.column :address, :string
      t.column :city, :string
      t.column :state, :string
      t.column :home_phone, :string
      t.column :work_phone, :string
      t.column :cell_phone, :string
      t.column :relationship, :string
      t.column :email, :string
    end
  end

  def self.down
    drop_table :caregivers
  end
end



class CreateCallOrders < ActiveRecord::Migration
  def self.up
    create_table :call_orders do |t|
      t.column :user_id, :integer
      t.column :caregiver_id, :integer
      t.column :position, :integer
    end
  end

  def self.down
    drop_table :call_orders
  end
end


class CreateUsers < ActiveRecord::Migration
  def self.up
    create_table "users", :force => true do |t|
      t.column :login,                     :string
      t.column :email,                     :string
      t.column :crypted_password,          :string, :limit => 40
      t.column :salt,                      :string, :limit => 40
      t.column :created_at,                :datetime
      t.column :updated_at,                :datetime
      t.column :remember_token,            :string
      t.column :remember_token_expires_at, :datetime

      t.column :activation_code, :string, :limit => 40
      t.column :activated_at, :datetime
    end
  end

  def self.down
    drop_table "users"
  end
end


Thanks for the help!
Chirag


--~--~---------~--~----~------------~-------~--~----~
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
-~----------~----~----~----~------~----~------~--~---

Michael Wang

2007-Oct-04 05:33 UTC

head link

Re: problem with has_many :through association

Migrations look fine and it''s working for me:

 >> call_list = User.find(1)
=> #<User:0x3447480 @attributes={"salt"=>nil,
"activated_at"=>nil,
"updated_at"=>"2007-10-03 22:25:01",
"crypted_password"=>nil,
"activation_code"=>nil,
"remember_token_expires_at"=>nil, "id"=>"1",
"remember_token"=>nil, "login"=>"test",
"created_at"=>"2007-10-03
22:25:01", "email"=>nil}>
 >> call_list.call_orders.each do |call_order|
?> puts call_order.caregiver.first_name
 >> end
John


 >> call_list.call_orders[0].caregiver
=> #<Caregiver:0x3441634 @attributes={"work_phone"=>nil,
"city"=>nil,
"id"=>"1", "relationship"=>nil,
"cell_phone"=>nil, "home_phone"=>nil,
"first_name"=>"John", "address"=>nil,
"last_name"=>"Smith",
"email"=>nil, "state"=>nil}>

My guess is you have some bad data somewhere.


--
Michael Wang

--~--~---------~--~----~------------~-------~--~----~
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
-~----------~----~----~----~------~----~------~--~---

Pablo Castellazzi

2007-Oct-04 08:26 UTC

head link

Re: problem with has_many :through association

Im agree with Michael.

Btw, you can improve your code with a nested :include option like
this:
@call_list = User.find(params[:id], :include => [ { :call_orders
=> :caregiver } ])

Take a look at this: http://snippets.dzone.com/posts/show/2089 for a
better
explanation.

Regards.
Pablo Castellazzi.

On Oct 2, 8:50 pm, chirag
<patel...-/E1597aS9LQAvxtiuMwx3w@public.gmane.org>
wrote:> I have the following models
>
>    1. class Caregiver < ActiveRecord::Base
>    2.   has_many :call_orders
>    3.   has_many :users, :through => :call_orders
>    4. end
>    5.
>    6. class User < ActiveRecord::Base
>    7.   has_many :call_orders, :order => :position
>    8.   has_many :caregivers, :through => :call_orders
>    9. end
>   10.
>   11. class CallOrder < ActiveRecord::Base
>   12.   belongs_to :user
>   13.   belongs_to :caregiver
>   14.   acts_as_list :scope => :user
>   15. end
>
> When I run the following commands, I get an error:
>
>    1. @call_list = User.find(params[:id])
>    2. @call_list.call_orders.each do |call_order|
>    3. puts call_order.caregiver.first_name
>
> This is the error:
>
>    You have a nil object when you didn''t expect it!
>    The error occurred while evaluating nil.first_name

--~--~---------~--~----~------------~-------~--~----~
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
-~----------~----~----~----~------~----~------~--~---

Frederick Cheung

2007-Oct-04 11:43 UTC

head link

Re: problem with has_many :through association

On 3 Oct 2007, at 02:50, chirag wrote:>
> When I run the following commands, I get an error:
>
>    1. @call_list = User.find(params[:id])
>    2. @call_list.call_orders.each do |call_order|
>    3. puts call_order.caregiver.first_name
>
>
> This is the error:
>
>    You have a nil object when you didn''t expect it!
>    The error occurred while evaluating nil.first_name
>Is that just the way the data is? caregiver is belongs_to of  
callorder: call_order.caregiver can be nil (unless you''ve got other  
contraints that forbid it)

Fred

--~--~---------~--~----~------------~-------~--~----~
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
-~----------~----~----~----~------~----~------~--~---

Pablo Castellazzi

2007-Oct-04 17:09 UTC

head link

Re: problem with has_many :through association

> Is that just the way the data is? caregiver is belongs_to of
> callorder: call_order.caregiver can be nil (unless you''ve got
other
> contraints that forbid it)
Freederick mades a good point here. If nil values are accepted as your
model definition suggests, then you should use a "compacted" list of
caregivers like:

@call_list.call_orders.collect(&:caregiver).compact.each do |
caregiver|
  puts caregiver.first_name
end

if nil values are not accepted you should add valitadates_presence_of
and validates_associated to force a caregiver to be present:

class CallOrder < ActiveRecord::Base
   belongs_to :user
   belongs_to :caregiver
   acts_as_list :scope => :user

   validates_presence_of :caregiver_id
   validates_associated :caregiver
end

Regards
Pablo Castellazzi.


--~--~---------~--~----~------------~-------~--~----~
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
-~----------~----~----~----~------~----~------~--~---

Rails - Oct 2007 - problem with has_many :through association

problem with has_many :through association

Re: problem with has_many :through association

Re: problem with has_many :through association

Re: problem with has_many :through association

Re: problem with has_many :through association

Re: problem with has_many :through association

Re: problem with has_many :through association