Rails 3 validate uniqueness of one value against a column?

I have a model with an active column, which is a boolean. I want to validate the uniqueness of all newly added records against company_id, such that I can add as many records as I want with the same company_id to the table so long as active is set to false. There should only be one active record for each company_id.

How would I write this? I've already tried:

validates :company_id, :uniqueness => { :scope => :active }

But that seems to also validate against unique combinations of active being false (such that I can never have more than two company_id's in the table with the same active status, regardless of what active is)--the validation above allows two records for company_id, one with active = false and the other with active = true. Once those two records are in, the validation blocks everything else.

I then tried adding this:

scope :active, where(:active => true)

But that doesn't seem to have changed the va开发者_JAVA技巧lidation at all (same issue as above).

How can I write this validation so that I can add as many records with the same company_id so long as active is false, and only allowing one active = true per company_id?

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No need to use validates_each - that's only if you want to pass multiple attributes through the same block. Just create a custom validation:

validate :company_id_when_active

def company_id_when_active
  if active? and CompanyTerm.exists? ["company_id = ? AND active = 1 AND id != ?", company_id, id.to_i]
    errors.add( :company_id, 'already has an active term')
  end
end

---

Rails 4+ offers a much better solution for this.

  validates_uniqueness_of :company_id, conditions: -> { where(active: true) }

check out documentation

---

Ok, I think I finally figured this out.

Checking up on Rails Guides led me to validates_each, which led me to this solution:

scope :active, where(:active => true)

validates_each :company do |model, attr, value|
  active = CompanyTerm.active.where(:company_id => value)
  model.errors.add(attr, 'already has an active term') unless active.empty?
end

I don't know if that's the most efficient way to write this, but it works. I'm open to any and all suggestions!

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Old topic, but there is the simpliest solution. The answer above is almost correct. You can use :if statement as a key like:

validates :active, :uniqueness => { :scope => :company_id }, :if => :active

---

Using @raj answer with validates method:

validates(
    :company_id,
    uniqueness: { conditions: -> { where(active: true) } }
  )

---

validates :company_id, :uniqueness => { :scope => :active } unless Proc.new { self.active }

And maybe you want to call company itself

validates :company, :uniqueness => { :scope => :active } unless Proc.new { self.active }

EDIT

Following answer based on your solution is a bit more efficient:

scope :active, where(:active => true)

validates_each :company do |model, attr, value|
  model.errors.add(attr, 'already has an active term') if CompanyTerm.active.exists?(:company_id => value)
end