I'm working on an RoR project and I'd like to have a uniqueness validation on one of my models that checks against a custom scope:
class Keyword < ActiveRecord::Base
belongs_to :keyword_list
scope :active, -> { where("expiration > ?", DateTime.now) }
validates :name, uniqueness: { scope: [:active, :keyword_list_id] }
end
Only, this doesn't work. It checks the database for an active column, which doesn't exist and throws this error:
ActiveRecord::StatementInvalid: PG::UndefinedColumn: ERROR: column keywords.active does not exist
So, my question is there any way to make this work, or do I have to write a custom validator? And if so, are there any tips on what it should look like to hitting the database too much?
No, you will have to write a custom validation.
Try this.
# In app/models/keyword.rb
validate :freshness
private
def freshness
if Keyword.active.find_by(name: self.name, keyword_list_id: self.keyword_list_id)
errors.add(:base, "Name is not fresh enough.") # Fails the validation with error message
end
end
Here's another interesting point, you cannot rely on validates_uniqueness_of, or any other uniqueness validator in rails, because validations are not run atomically, meaning that if two identical records are inserted at the same time, and there is no SQL constraint validating uniqueness, the ruby validations will pass and both records will be inserted.
What I'm trying to say here is that if your validations are mission-critical, use a SQL constraint.
Related
I have a Company model and an Employer model. Employer belongs_to :company and Company has_many :employers. Within my Employer model I have the following validation:
validates :company_id, inclusion: {in: Company.pluck(:id).prepend(nil)}
I'm running into a problem where the above validation fails. Here is an example setup in a controller action that will cause the validation to fail:
company = Company.new(company_params)
# company_params contains nested attributes for employers
company.employers.each do |employer|
employer.password = SecureRandom.hex
end
company.employers.first.role = 'Admin' if client.employers.count == 1
company.save!
admin = company.employers.where(role: 'Admin').order(created_at: :asc).last
admin.update(some_attr: 'some_val')
On the last line in the example code snippet, admin.update will fail because the validation is checking to see if company_id is included in the list, which it is not, since the list was generated before company was saved.
Obviously there are ways around this such as grabbing the value of company.id and then using it to define admin later, but that seems like a roundabout solution. What I'd like to know is if there is a better way to solve this problem.
Update
Apparently the possible workaround I suggested doesn't even work.
new_company = Company.find(company.id)
admin = new_company.employers.where(role: 'Admin').order(created_at: :asc).last
admin.update
# Fails validation as before
I'm not sure I understand your question completely, but there is an issue in this part of the code:
validates :company_id, inclusion: {in: Company.pluck(:id).prepend(nil)}
The validation is configured on the class-level, so it won't work well with updates on that model (won't be re-evaluated on subsequent validations).
The docs state that you can use a block for inclusion in, so you could try to do that as well:
validates :company_id, inclusion: {in: ->() { Company.pluck(:id).prepend(nil) }}
Some people would recommend that you not even do this validation, but instead, have a database constraint on that column.
I believe you are misusing the inclusion validator here. If you want to validate that an associated model exists, instead of its id column having a value, you can do this in two ways. In ActivRecord, you can use a presence validator.
validates :company, presence: true
You should also use a foreign key constraint on the database level. This prevents a model from being saved if there is no corresponding record in the associated table.
add_foreign_key :employers, :companies
If it gets past ActiveRecord, the database will throw an error if there is no company record with the given company_id.
I would like to perform a uniqueness validation on a hstore field.
When I set is as:
class User
store_accessor :attributes, :foo_attr
validates :foo_attr, uniqueness: true
end
I get undefined method 'limit' for nil:NilClass
In a Rails issue store_accessor and uniqueness validation? user al2o3cr explains:
validates_uniqueness_of is not going to work in this case - it's
expecting a database column named stripe_id. With an Hstore column
it's technically possible to perform the required query, but the
resulting SQL is only applicable to that storage format and only works
on Postgres.
In your case, a custom subclass of
ActiveRecord::Validations::UniquenessValidator with an overridden
build_relation would probably be a better choice.
How would you go around creating that custom validator?
I already have a database level uniqueness set up as explained in Race condition using Postgres hstore all I need now is to make valid? return false on the same foo_attr.
If you're going to the trouble of setting up a custom hstore index and writing a custom validation, my first instinct is that maybe you want foo_attr to be a column of its own.
As for a custom validation, it's pretty straightforward:
validate :foo_attr_uniqueness
def foo_attr_uniqueness
if self.class.where(foo_attr: foo_attr) # Same foo_attr
.where.not(id: id) # On a different record
.exists?
errors.add(:foo_attr, 'must be unique')
end
end
I have two models: event.rb and bag.rb
An event has an attribute called slug and a bag has an attribute called bag_code.
I generate a view based on the bag_code attribute. E.g. if the bag-code is "4711" I load records based on that code.
Now for some occasions, a user can define a slug URL in an event and in this case it should overwrite the bag-code.
What I don't want is that a user can choose a slug with a value which is already a bag_code (in this case it should be forbidden to choose the slug "4711") as this would cause troubles in my view, so it has to be unique in two models attributes.
I tried to solve this via scope
validates_uniqueness_of :slug, scope: [:bag_code]
but that would only work within the same model.
The association between my models is:
event.rb
has_many :bags
A custom validation method would work for this case. Here is how you would set it up:
event.rb
validates :slug, uniqueness: true
validate :slug_is_unique_from_bag_codes
private
def slug_is_unique_from_bag_codes
if Bag.find_by bag_code: slug
errors.add :base, "The slug is already being used as a bag code"
end
end
I have a Rails 3.2.18 app where I'm trying to do some conditional validation on a model.
In the call model there are two fields :location_id (which is an association to a list of pre-defined locations) and :location_other (which is a text field where someone could type in a string or in this case an address).
What I want to be able to do is use validations when creating a call to where either the :location_id or :location_other is validated to be present.
I've read through the Rails validations guide and am a little confused. Was hoping someone could shed some light on how to do this easily with a conditional.
I believe this is what you're looking for:
class Call < ActiveRecord::Base
validate :location_id_or_other
def location_id_or_other
if location_id.blank? && location_other.blank?
errors.add(:location_other, 'needs to be present if location_id is not present')
end
end
end
location_id_or_other is a custom validation method that checks if location_id and location_other are blank. If they both are, then it adds a validation error. If the presence of location_id and location_other is an exclusive or, i.e. only one of the two can be present, not either, and not both, then you can make the following change to the if block in the method.
if location_id.blank? == location_other.blank?
errors.add(:location_other, "must be present if location_id isn't, but can't be present if location_id is")
end
Alternate Solution
class Call < ActiveRecord::Base
validates :location_id, presence: true, unless: :location_other
validates :location_other, presence: true, unless: :location_id
end
This solution (only) works if the presence of location_id and location_other is an exclusive or.
Check out the Rails Validation Guide for more information.
Hi I wan't to validate the unique combination of 3 columns in my table.
Let's say I have a table called cars with the values :brand, :model_name and :fuel_type.
What I then want is to validate if a record is unique based on the combination of those 3. An example:
brand model_name fuel_type
Audi A4 Gas
Audi A4 Diesel
Audi A6 Gas
Should all be valid. But another record with 'Audi, A6, Gas' should NOT be valid.
I know of this validation, but I doubt that it actually does what I want.
validates_uniqueness_of :brand, :scope => {:model_name, :fuel_type}
There is a syntax error in your code snippet. The correct validation is :
validates_uniqueness_of :car_model_name, :scope => [:brand_id, :fuel_type_id]
or even shorter in ruby 1.9.x:
validates_uniqueness_of :car_model_name, scope: [:brand_id, :fuel_type_id]
with rails 4 you can use:
validates :car_model_name, uniqueness: { scope: [:brand_id, :fuel_type_id] }
with rails 5 you can use
validates_uniqueness_of :car_model_name, scope: %i[brand_id fuel_type_id]
Depends on your needs you could also to add a constraint (as a part of table creation migration or as a separate one) instead of model validation:
add_index :the_table_name, [:brand, :model_name, :fuel_type], :unique => true
Adding the unique constraint on the database level makes sense, in case multiple database connections are performing write operations at the same time.
To Rails 4 the correct code with new hash pattern
validates :column_name, uniqueness: {scope: [:brand_id, :fuel_type_id]}
I would make it this way:
validates_uniqueness_of :model_name, :scope => {:brand_id, :fuel_type_id}
because it makes more sense for me:
there should not be duplicated "model names" for combination of "brand" and "fuel type", vs
there should not be duplicated "brands" for combination of "model name" and "fuel type"
but it's subjective opinion.
Of course if brand and fuel_type are relationships to other models (if not, then just drop "_id" part). With uniqueness validation you can't check non-db columns, so you have to validate foreign keys in model.
You need to define which attribute is validated - you don't validate all at once, if you want, you need to create separate validation for every attribute, so when user make mistake and tries to create duplicated record, then you show him errors in form near invalid field.
Using this validation method in conjunction with ActiveRecord::Validations#save does not guarantee the absence of duplicate record insertions, because uniqueness checks on the application level are inherently prone to race conditions.
This could even happen if you use transactions with the 'serializable' isolation level. The best way to work around this problem is to add a unique index to the database table using ActiveRecord::ConnectionAdapters::SchemaStatements#add_index. In the rare case that a race condition occurs, the database will guarantee the field's uniqueness.
Piecing together the other answers and trying it myself, this is the syntax you're looking for:
validates :brand, uniqueness: { scope: [:model_name, :fuel_type] }
I'm not sure why the other answers are adding _id to the fields in the scope. That would only be needed if these fields are representing other models, but I didn't see an indication of that in the question. Additionally, these fields can be in any order. This will accomplish the same thing, only the error will be on the :model_name attribute instead of :brand:
validates :model_name, uniqueness: { scope: [:fuel_type, :brand] }