Rails: How to fix issue with unique number under scope that doesn’t count correctly with find_or_create_by

The bug fixing was very frustrating. Take a look at the following example:

class Model < ActiveRecord::Base
...
  # Set a unique scoped number
  validate do
    errors.add(:scoped_unique, "is already taken") if parent_parent_model.parent_model.models(true).where(scoped_unique: scoped_unique).where.not(id: id).present?
  end
  before_validation on: :create do
    self.scoped_unique = (parent_parent_model.parent_model.models(true).collect { | model | model.scoped_unique }.max.to_i || 0) + 1 if self.scoped_unique.nil?
  end
...
end

This works just fine when you are creating a new model like this:

parent_model.models.create(...)

However using find_or_create_by it adds unexpectedly additional parameters to the scope the model itself with the parent_model (thus not restricting itself to parent_parent_model only)!

parent_model.models.create_with(...).find_or_create_by(...)

Turns out you have to unscope the whole query:

class Model < ActiveRecord::Base
...
  # Set a unique scoped number
  validate do
    Model.unscoped do
      errors.add(:scoped_unique, "is already taken") if parent_parent_model.parent_model.models(true).where(scoped_unique: scoped_unique).where.not(id: id).present?
    end
  end
  before_validation on: :create do
    Model.unscoped do
      self.scoped_unique = (parent_parent_model.parent_model.models(true).collect { | model | model.scoped_unique }.max.to_i || 0) + 1 if self.scoped_unique.nil?
    end
  end
...
end

The Author

Dan Schultzer is an active experienced entrepreneur, starting the Being Proactive groups, Dream Conception organization, among other things. You can find him at twitter

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