Question

I’m having a problem instantiating a ListItem object with specified attributes. For some reason all attributes are set to nil even if I specify values. However, if I specify attributes for a List, they retain their values.

Attributes for a List retain their values:

>> list = List.new(:id => 20, :name => "Test List")
=> #<List id: 20, name: "Test List">

Attributes for a ListItem don’t retain their values:

>> list_item = ListItem.new(:id => 17, :list_id => 20, :name => "Test Item")
=> #<ListItem id: nil, list_id: nil, name: nil>

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UPDATE #1:

I thought the id was the only attribute not retaining its value but realized that setting any attribute for a ListItem gets set to nil.

---

UPDATE #2:

I added validates_associated :list_items to the List class which alleviated an error regarding the name attribute being blank.

However, I still can’t explicitly assign an id to a new ListItem.

---

list.rb:

class List < ActiveRecord::Base
    has_many :list_items, :dependent => :destroy

    accepts_nested_attributes_for :list_items, 
                                  :reject_if => lambda { |a| a[:name].blank? }, 
                                  :allow_destroy => true
end

list_item.rb:

class ListItem < ActiveRecord::Base
    belongs_to :list

    validates_presence_of :name  
end

schema.rb

ActiveRecord::Schema.define(:version => 20100506144717) do

  create_table "list_items", :force => true do |t|
    t.integer  "list_id"       
    t.string   "name"       
    t.datetime "created_at"
    t.datetime "updated_at"
  end

  create_table "lists", :force => true do |t|
    t.string   "name"        
    t.datetime "created_at"
    t.datetime "updated_at"        
  end

end

Answer 1

I created your models and tables in my local setup. I didn’t encounter any errors. There must be some class name conflict OR you have some before_save filters/observers resetting the values.

Note

I would change the model names to be bit more specific. It is very easy to run in to class name conflicts with names like List and ListItem