(Object doesn't support #inspect) - ruby-on-rails-3.1

Question

I have a simple case, involving two model classes:
class Game < ActiveRecord::Base
has_many :snapshots
def initialize(params={})
# ...
end
end
class Snapshot < ActiveRecord::Base
belongs_to :game
def initialize(params={})
# ...
end
end
with these migrations:
class CreateGames < ActiveRecord::Migration
def change
create_table :games do |t|
t.string :name
t.string :difficulty
t.string :status
t.timestamps
end
end
end
class CreateSnapshots < ActiveRecord::Migration
def change
create_table :snapshots do |t|
t.integer :game_id
t.integer :branch_mark
t.string :previous_state
t.integer :new_row
t.integer :new_column
t.integer :new_value
t.timestamps
end
end
end
If I attempt to create a Snapshot instance in rails console, using
Snapshot.new
I get
(Object doesn't support #inspect)
Now for the good part. If I comment out the initialize method in snapshot.rb, then Snapshot.new works. Why is this happening?
BTW I am using Rails 3.1, and Ruby 1.9.2

Answer 1

This is happening because you override the initialize method of your base class (ActiveRecord::Base). Instance variables defined in your base class will not get initialized and #inspect will fail.
To fix this problem you need to call super in your sub class:
class Game < ActiveRecord::Base
has_many :snapshots
def initialize(params={})
super(params)
# ...
end
end

Answer 2

I had this symptom when I had a serialize in a model like this;
serialize :column1, :column2
Needs to be like;
serialize :column1
serialize :column2

Answer 3

I ran into this issue when I used an invalid association name in a joins.
For example,
Book.joins(:authors).first
Should be
Book.joins(:author).first
Assuming a Book model belongs_to an Author model.

Answer 4

This can also happen when you implement after_initialize, particularly if you are attempting to access attributes which were not included in your select. For instance:
after_initialize do |pet|
pet.speak_method ||= bark # default
end
To fix, add a test for whether the attribute exists:
after_initialize do |pet|
pet.speak_method ||= bark if pet.attributes.include? 'speak_method' # default`
end

Answer 5

I'm not sure exactly why, but I got this error when I accidentally misspelled 'belongs_to' as 'belong_to' in the associated class definition.

Answer 6

I believe you forgot to
rails db:migrate

Answer 7

Try calling .valid? on the new object to see if you can get a more helpful error.
In my case, I got this error from a block of code that creates a new instance of one of my models and assigns values to its fields. It turns out that my code was assigning a value to one of the fields that Rails couldn't match with that field's type. Calling valid? on the new object gave me a more helpful error (undefined method `to_f' for #<MatchData...).

Answer 8

I ran into this problem after trying to integrate devise authentication with an existing User model, I solved it by running command below:
$spring stop
Don't know the exact cause but hope it helps someone.

Answer 9

This is a misleading and nonspecific error. For instance, I just got it because I made a scope like this:
scope :posted, -> { where('posted_on_date <= ?', Date.today) }
when it should have been:
scope :posted, -> { where('post_on_date <= ?', Date.today) }
In my case, this was due to my mistakenly using the posted_on_date attribute.

Answer 10

I get this problem if the model contains an after_find.

Answer 11

The same error if you put the attribute type wrong:
attribute :publicar, :integer, default: true
instead of
attribute :publicar, :boolean, default: true

Answer 12

I was getting this error when running an ActiveRecord .where clause/method.
It was simply because there was a typo in the column name. Once I fixed the typo the query worked exactly as expected.
Wrong:
Package.where(scrape_nunber: 2)
Right (fixed typo in column name, and it works now):
Package.where(scrape_number: 2)
Just double check there isn't a typo in your column name(s) in the where clause.