More than 3 hours I am trying to solve pretty easy error (on the first glance):
undefined method `empty?' for nil:NilClass
but still no success.
I have the DB table products, which contains the columns category_id and manufacturer_id.
Associations:
class Product < ActiveRecord::Base
belongs_to :manufacturer
belongs_to :category
...
end
class Category < ActiveRecord::Base # the same for Manufacturer
has_ancestry
has_many :products
end
Trying to grab some data:
Product.where('category_id IS NOT NULL AND manufacturer_id IS NOT NULL').each do |product|
...
puts product.manufacturer.name # here's the error
puts product.category.name # here's the error
...
end
I fetched all rows, where is not NIL value in the columns manufacturer_id and category_id... so how can I get this error?
Also, I've tried:
...
puts product.manufacturer.name unless product.manufacturer_id.nil?
puts product.category.name unless product.category_id.nil?
...
What am I doing wrong?
You most likely deleted a manufacturer or category so there's no corresponding record to match the foreign key.
Problably is a business logic problem on your database considering your query.
IMHO u are calling some objects that will not be valid ones. Check your database to see if all registers attend your validations logic.
Related
I am building a Sinatra API. My models use ActiveRecord and have a many-to-many model relationship.
class Workout < ActiveRecord::Base
has_many :workouts_exercises, dependent: :destroy
has_many :exercises, through: :workouts_exercises
end
class Exercise < ActiveRecord::Base
has_many :workouts_exercises
has_many :workouts, through: :workouts_exercises
end
class WorkoutsExercises < ActiveRecord::Base
belongs_to :workouts
belongs_to :exercises
end
I am trying to set up FactoryGirl to use these associations. Here is what I've got from reading all the docs I have found so far.
FactoryGirl.define do
factory :workout do
name 'Default Workout Factory Name'
description 'Default Workout Factory Description'
factory :workout_with_exercises do
after(:create) do |workout|
workout.exercises << FactoryGirl.create(:exercise)
end
end
end
end
FactoryGirl.define do
factory :exercise do
name 'Default Exercise Factory Name'
description 'Default Exercise Factory Description'
end
end
FactoryGirl.define do
factory :workouts_exercises do
workout
exercise
end
end
Here is my test that I would like to run
it 'returns the associated exercises' do
workout = FactoryGirl.create(:workout_with_exercises)
associated_exercises = workout.exercises
expect(associated_exercises.count).to eq(1)
end
However, when I run the specs I receive
1) Workout returns the associated exercises
Failure/Error: workout.exercises << FactoryGirl.create(:exercise)
NameError:
uninitialized constant Workout::WorkoutsExercise
The first method of debugging I tried was to pry before workout= declaration. Workout doesn't know about the exercises attribute. According to the ActiveRecord documentation, setting up a many-to-many association should provide you with the 16 #collection methods. This would mean that #exercises should return all the associated Exercise objects for the Workout object.
I can't, for the life of me, figure out whether or not it's my AR associations in the models that are to blame - or the FactoryGirl configuration I have. I've checked the SQL tables and all of the columns seem to be appropriate. I could really use some help figuring out what the issue is.
I've tried a few other FactoryGirl after_create hooks, using the shovel operator and attempting to declare the workouts_exercises association explicitly:
workout.exercises << [
create(:exercise, name: 'Bench Press', workouts_exercises: workout),
create(:exercise, name: 'Pushups', workouts_exercises: workout),
create(:exercise, name: 'DB Flys', workouts_exercises: workout)
]
Again, failure.
My third attempt was to use the FactoryGirl callback methods from ThoughtBot - ain't no calla back girl.
factory :workout_with_exercises do
after(:create) do |workout|
FactoryGirl.create(:exercise, workout: workout)
end
end
This results in
undefined method `exercise=' for #<Workout:0x007ff6250c2768>
Which makes me believe the AR associations aren't written correctly.
Thanks in advance for any help you can lend!
I use Sinatra, ActiveRecord, and RSpec. Just recently, I added FactoryGirl to the mix.
In your test framework's initialization point (I use RSpec, which is spec_helper.rb), you'll need to require the file that contains your model classes.
Next, do your model classes live within a module?
My model classes don't exist at the top-level, because I instead put them in a module for better organization within the project.
With this pattern, I found that I needed to explicitly define the module + class path for FactoryGirl.
The following would not work:
FactoryGirl.define do
factory :vendor do
name 'Test Vendor
end
end
But things began to work after I told FactoryGirl the full class name, like below:
FactoryGirl.define do
factory :vendor, class: MyAppName::Models::Vendor do
name 'Test Vendor
end
end
Using: Rails 4.1.4, PostgreSQL 9.1.13
Hi. I'm have a simple problem, but for some reason I can't get it done. The picture is this:
Models
class Article < ActiveRecord::Base
belongs_to :user
has_many :votes
end
class User < ActiveRecord::Base
has_many :articles
has_many :votes
end
class Vote < ActiveRecord::Base
belongs_to :article
belongs_to :user, scope: :hotel_id
validates_inclusion_of :value, in: 0..5
validates_uniqueness_of :user_id, :article_id
end
Idea
Each User can Vote for each Article but only once (to avoid multiple voting).
Vote model has a 'value' attribute that is the range 0..10.
ArticlesController except standard CRUD methods has action #showcase which must return 5 articles with the top votes rating from the DB and sort them in the descending order (and render the respective view).
So I understand that the proper way is to write the class method in the Article Model (smth. like "by_top_votes") and use it in the ArticlesController#showcase:
def showcase
#top_five_articles = Article.by_top_votes
end
The problem is that I can't write the proper query to the DB which will: 1)find articles, 2)find all votes of the each article, 3) sum all values of the respective article's votes, 4)sort them (this step I know how to do).
Thank you for reading and for the help.
P.S. Maybe my way to solve problem is almost wrong. If this so, please tell my the right one.
Ok, I've done it by myself. If anybody will stuck with the same problem, here is solution for it.
1. In Vote model summarize the vote's values:
def self.sum_value
sum(:value)
end
2. Add new attribute (and column) to Article - user_rating:integer.
3. In the Article model define two class methods:
# assign user_rating attribute with the sum of all votes values
def set_user_rating
user_rating = self.votes.sum_value
self.update_attribute(:user_rating, user_rating)
end
# get top 5 articles by user_rating value from db
def self.top_by_user_rating
Article.order(:user_rating).reverse_order.limit(5)
end
4. In the ArticlesController define showcase action:
def showcase
#top_articles = Article.top_by_user_rating
end
5. In the VotesController define create action:
def create
#article = Article.find(params[:article_id])
#vote = #article.votes.create(vote_params)
if #vote.save
#article.set_user_rating
redirect_to #article, notice: "Thanks for your vote"
else
.
end
end
It works and tests are passing.
In a sample Rails 3.2.8 app (on Ruby 1.9.3) there is the following simple setup:
class Account < ActiveRecord::Base
has_many :line_items
def subtotal
line_items.sum(&:price)
end
end
class Line_Item < ActiveRecord::Base
belongs_to :product
def price
product.price * time
end
end
account = Account.new
account.line_items.build do |item|
item.years = 4
item.product = Product.last
end
account.subtotal
#=> TypeError: nil can't be coerced into BigDecimal
As above the subtotal method fails with a conversion error. In subtotal I checked the type returned by line_items.class and got Array. If I update the definition of subtotal to either of the following, the method works:
line_items.to_a.sum(&:price)
#=> #<BigDecimal:7ff4d34ca7c8,'0.0',9(36)>
line_items.map(&:price).sum
#=> #<BigDecimal:7ff4d3373b40,'0.0',9(36)>
Why does the initial definition of line_items.sum(&:price) fail?
This appears to be a bug in Rails (at least in 3.2.8).
In Rails 3.2.8, the has_many association is dynamically defining collection.sum.
Though this isn't reflected in A Guide to Active Record Associations
or ActiveRecord::Associations::ClassMethods API docs; it is briefly listed in the API under the "Collection associations (one-to-many / many-to-many)"
chart, but not referenced again.
According to the code, it will always try to hit the database using a SQL sum.
However, in this particular instance, the model isn't saved. So there's nothing
in the database.
So to clear that up a little:
account.line_items.sum(&:price) # Uses Collection#sum, goes to database
account.line_items.map.sum(&:price) # Uses Enumerable#map then Enumerable#sum
This has been logged under issue #7928; which appears related to issue #5215: "finders and scopes on has_many association on new object incorrectly query db for null foreign keys".
This looks like it should be something pretty easy but I can't seem to get it to work. I have a model with a has_many relationship and I'd like a scope on the parent that allows me to select only certain attributes for each.
An example:
class Bakery < ActiveRecord::Base
has_many :pastries
scope :summary, select([:id, :name, 'some option calling pastries.summary'])
class Pastry < ActiveRecord::Base
belongs_to :bakery
scope :summary, select([:id, :image_url])
I'd like to be able to call something like Bakery.first.summary and get a Bakery model with only the id and name populated and for each pastry in it's pastries array to only have the id and image_url attributes populated.
You could do this, but it won't affect the SQL queries that are made as a result (assuming you're trying to optimise the underlying query?):
class Pastry
...
def summary
{
:id => self.id,
:image_url => self.image_url
}
end
end
class Bakery
...
def summary
pastries.collect {|i| i.summary }
end
end
This would then give you an array of hashes, not model instances.
ActiveRecord doesn't behave how you're expecting with models - it will fetch whatever data it thinks you need. You could look at using the Sequel gem instead, or executing a raw SQL query such as:
Pastry.find_by_sql("SELECT id, name from ...")
But this could give you unexpected behaviour.
Consider the following parent/child relationship where Parent is 1..n with Kids (only the relevant stuff here)...
class Parent < ActiveRecord::Base
# !EDIT! - was missing this require originally -- was the root cause!
require "Kid"
has_many :kids, :dependent => :destroy, :validate => true
accepts_nested_attributes_for :kids
validates_associated :kids
end
class Kid < ActiveRecord::Base
belongs_to :parent
# for simplicity, assume a single field: #item
validates_presence_of :item, :message => "is expected"
end
The validates_presence_of methods on the Kid model works as expected on validation failure, generating a final string of Item is expected per the custom message attribute supplied.
But if try validates_with, instead...
class Kid < ActiveRecord::Base
belongs_to :parent
validates_with TrivialValidator
end
class TrivialValidator
def validate
if record.item != "good"
record.errors[:base] << "Bad item!"
end
end
end
...Rails returns a NameError - uninitialized constant Parent::Kid error following not only an attempt to create (initial persist) user data, but also when even attempting to build the initial form. Relevant bits from the controller:
def new
#parent = Parent.new
#parent.kids.new # NameError, validates_* methods called within
end
def create
#parent = Parent.new(params[:parent])
#parent.save # NameError, validates_* methods called within
end
The error suggests that somewhere during model name (and perhaps field name?) resolution for error message construction, something has run afoul. But why would it happen for some validates_* methods and not others?
Anybody else hit a wall with this? Is there some ceremony needed here that I've left out in order to make this work, particularly regarding model names?
After a few hours away, and returning fresh -- Was missing require "Kid" in Parent class. Will edit.