I am storing an array of typed objects in an ActiveRecord model like:
class Store::Bin < ActiveRecord::Base
serialize :items, Array
end
class Store::Item
include Virtus.model
attribute :name, String
...
end
When I make a code change in development mode and refresh my browser, I get an undefined class/module Store::Item exception.
It seems like something is getting crossed up with the class loading. All files are in the app/models/store/... directory, properly named w/r to their camelcase name.
The same issue happens when using the rails console. reload! does not fix the issue in the console; instead I have to exit and restart the console.
Adding a type to the array seemed to solve the problem.... but caused an issue with the associated FactoryGirl factory.
class Store::Bin < ActiveRecord::Base
serialize :items, Array[Store::Item]
end
UPDATE: the real issue was that when a code change is made to store/bin.rb, that class gets auto-loaded, but the auto loader had no idea that Store::Item was a dependency.
THE REAL FIX: Declare the required dependency using require_dependency
require_dependency "store/item"
class Store::Bin < ActiveRecord::Base
serialize :items, Array
end
You should avoid the :: operator when defining classes because of Rails autoload problems. Instead, try
module Store
class Item
# ...
end
end
When you're not sure what's going on you can use Module.nesting to figure out how Rails interprets the hierarchy.
Related
I'm trying to manually add data to a table in rails using the rails console, but I keep getting a undefined local variable or method error.
The model is namespaced under ratings:
models/ratings/value_for_money_score.rb
class Ratings::ValueForMoneyScore < ApplicationRecord
end
To try and manually add a record to the database, I run the following in the console:
$ RatingsValueForMoneyScore.create(score: '1', description:"Terrible, definitely not worth what was paid!")
And I get this error: NameError: uninitialized constant RatingsValueForMoneyScore
I have tried a few different versions such as
RatingsValueForMoneyScores.create,
Ratings_ValueForMoneyScores.create,
ratings_value_for_money_scores.create but keep getting the same error. What am I doing wrong?
Try
::ValueForMoneyScore.create(score: '1', description:"Terrible, definitely not worth what was paid!")
The error is descriptive enough in this case, the class RatingsValueForMoneyScore pretty much doesn't exist. Check your namespace, you have a class name (which should be singular) Rating, and the module ValueForMoneyScore. You'd use either
(after renaming the class to Rating)
Rating.create(...)
or
ValueForMoneyScores.create(...)
Your syntax is equivalent to:
class Rating
module ValueForMoneyScores < ApplicationRecord
...
end
end
The answer was a combination of input, so collecting that in one answer.
My namespaces weren't properly set up (I was using "Ratings" rather than "Rating"), so I fixed this for the tables. My models then looked as follows:
models/rating.rb
class Rating < ApplicationRecord
end
models/rating/value_for_money_score.rb
class Rating::ValueForMoneyScore < ApplicationRecord
end
And then this command worked for creating records in the rating_value_for_money_score table
$ Rating::ValueForMoneyScore.create(score: '1', description: "Test")
I have an application I'm building where I need one model to create instances of another model. I want every Car to have 4 tires.
Car model
class Car < ActiveRecord::Base
has_many :tires
after_create :make_tires
def make_tires
4.times { Tire.create(car: self.id) }
end
end
Tire model
class Tire < ActiveRecord::Base
belongs_to :car
end
However, inside of make_tires there is an error that there is no activerecord method for create or new if I try it for Tire. When I inspect Tire it doesn't have those methods.
How can I remedy this?
The error is this: undefined method 'create' for ActiveRecord::AttributeMethods::Serialization::Tire::Module
I have tested two environments: Testing and Development and they both fail for the same error.
It is a name conflict. Sit down and relax while I explain.
Solution with explanation:
In Ruby classes are just instances of class Class (which is a subclass of class Module). Instances of Module (including instances of Class) are quite weird objects, especially weird is their connection with ruby constants. You can create a new class at any point using standard ruby notation:
my_class = Class.new { attr_accessor :a }
instance = my_class.new
instance.a = 3
insatnce.a #=>
instance.class.name #=> nil
Well, our class has no name. It is just an anonymous class. How do classes get their name? By assigning it to a constant (for the first time):
MyClass = my_class
my_class.name #=> 'MyClass'
When you define class using a class keyword:
class MyClass
...
end
You just create a new instance of Class and assign it to a constant. Because of that, Ruby compiler seeing a constant has no idea whether it is a class or a number under it - it has to make a full search for that constant.
The logic behind finding a constant is quite complex and depends on the current nesting. Your case is quite simple (as there is no nesting), so ruby will try to find Tire class inside your class first and when failed it's subclasses and included modules.
Your problem is that your class inherits from ActiveRecord::Base (which is correct), which includes ActiveRecord::AttributeMethods::Serialization module, which defines Tire constant already. Hence, ruby will use this constant instead, as this is the best match for that name in given context.
To fix it, you must tell the compiler not to look within the current class but directly in the "top namespace" (which in ruby is Object. Seriously, try Object.constants) - you can do that using :: in front of your constant, like ::Tire.
Note: even though it works, this issue is a first warning for you that your code starts to smell. You should look after this ActiveRecord::AttributeMethods::Serialization::Tire::Module thingy as it seems you will encounter it more than once in the future.
Other stuff:
You can simplify your method slightly:
def make_tires
4.times { tires.create }
end
At that point you might encounter some error you had initially. If you do, then please find what is going on with that Tire::Module thing. If you don't care about the smell:
has_many :tires, class_name: '::Tire'
I'm not sure what's causing the exception you are seeing but you have a number of issues. First, you need to pass in a car instance instead of the id in make_tires. Like this:
def make_tires
4.times { Tire.create(car: self) }
end
You also need to have attr_accessible :car in the Tire model. Like this:
class Tire < ActiveRecord::Base
belongs_to :car
attr_accessible :car
end
I'm trying to do a pretty simple join in my model to list all 'Locations' in a 'Post' with a certain id.
Currently, each post has_many :locations, :through => :location_post. I'm using the 'blogit' gem, which puts posts in a module named 'Blogit::Posts'.
I'm getting a wrong argument type Class (expected Module) error when I try to run the following in my Post.rb model:
module Blogit
class Post < ActiveRecord::Base
before_save :reuse_existing_locations
def reuse_existing_locations
existing_locations = Location.include(Blogit::Post).first
end
How can I do a join through a module?
Thanks in advance!
I'm not sure I understand what you're trying to accomplish so just some notes and observations:
By looking at the code, it's clear that Blogit::Post is a class, not a module.
The include method takes modules (not classes), that's the error you're seeing.
You are calling the include method on the Location model and that seems kind
of strange to me. Did you mean to call includes? But then again that
wouldn't make much sense since it seems like you've got a many to many
relationship between Location and Blogit::Post.
In the Location model (which doesn't need to be in the Blogit namespace), you can simply reference the Blogit::Post model as
follows:
has_many :posts, class_name: "Blogit::Post", ...
If existing_locations is in fact an attribute on the model and you want to assign to it, you need to put self in front of it (as in self.existing_locations). Otherwise you're just creating a local variable.
You probably wanted to use ActiveModels includes instead of Rubys include, which is to include methods from another module.
I'm trying to get associations in FactoryGirl to work, and they just ... don't. I've basically got this:
class Foo
include Mongoid::Document
belongs_to :bar
end
class Bar
include Mongoid::Document
has_many :foos
end
FactoryGirl.define do
factory :foo, class => Foo do
bar
end
factory :bar, class => Bar do
end
end
At least so the docs lead me to believe... But then in my test, I have
a_foo=FactoryGirl.create :foo
a_foo.bar # Hooray! It's an associated object
Foo.where( _id: a_foo._id ).includes( :bar ).first.bar # This is nil!
Why is the associated value nil on the last line? I need it not to be, because the actual code being tested does this same thing, and it has a right to expect it to work... What am I missing about why this doesn't work right? Something to do with eager loading, perhaps?
Your code actually works for me with FactoryGirl 4.2.0, Mongoid 3.0.9. But I've run into similar issues when I've been running mongoid with the identitymap disabled (which is default behavior). Without the identitymap, you can have two different ruby objects representing the same document in the database, getting out of sync with each other. So, if you have autosave off, for example, this could cause the problem you're seeing.
Try pasting your simplified code into the rails console yourself -- if it works, then you probably changed something significant in pairing down your real code. (Sorry to point out the obvious, but the fact that you have a syntax error in your factory code makes me think you didn't actually test your sample code.)
Here's a Ruby OO head scratcher for ya, brought about by this Rails scenario:
class Product < ActiveRecord::Base
has_many(:prices)
# define private helper methods
end
module PrintProduct
attr_accessor(:isbn)
# override methods in ActiveRecord::Base
end
class Book < Product
include PrintProduct
end
Product is the base class of all products. Books are kept in the products table via STI. The PrintProduct module brings some common behavior and state to descendants of Product. Book is used inside fields_for blocks in views. This works for me, but I found some odd behavior:
After form submission, inside my controller, if I call a method on a book that is defined in PrintProduct, and that method calls a helper method defined in Product, which in turn calls the prices method defined by has_many, I'll get an error complaining that Book#prices is not found.
Why is that? Book is a direct descendant of Product!
More interesting is the following..
As I developed this hierarchy PrintProduct started to become more of an abstract ActiveRecord::Base, so I thought it prudent to redefine everything as such:
class Product < ActiveRecord::Base
end
class PrintProduct < Product
end
class Book < PrintProduct
end
All method definitions, etc. are the same. In this case, however, my web form won't load because the attributes defined by attr_accessor (which are "virtual attributes" referenced by the form but not persisted in the DB) aren't found. I'll get an error saying that there is no method Book#isbn. Why is that?? I can't see a reason why the attr_accessor attributes are not found inside my form's fields_for block when PrintProduct is a class, but they are found when PrintProduct is a Module.
Any insight would be appreciated. I'm dying to know why these errors are occurring!
You might have better luck delaying the attr_accessor call in PrintProduct until mixin-time:
module PrintProduct
def self.included(base)
base.attr_accessor :isbn
end
# other instance methods here
end
The problem is likely something to do with timing of the attr_accessor call and how that applies to modules mixed in. I'm not certain that the timing is defined by the Ruby spec, so it might vary betweeen implementations or versions.