Database model validation

Question

I want to add a validation in my model where I have 2 fields:

t.boolean :first
t.boolean :second

I want to ensure that when

first field is false

then

second field is always false

Is that possible?

Zepplock · Accepted Answer · 2011-07-22 17:39:22Z

2

You can do something like this in Rails3:

class MyValidator < ActiveModel::EachValidator
  def validate_each(object, attribute, value)
    unless {your condition here}
      object.errors[attribute] << (options[:message] || "your error here") 
    end
  end
end

Edit: Forgot to mention that this example is from Railscasts: http://railscasts.com/episodes/211-validations-in-rails-3 in case you need more detailed information on this topic

edited Jul 22, 2011 at 17:39

answered Jul 22, 2011 at 15:41

Zepplock

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2 Comments

glarkou Over a year ago

What is the advantage of using a new class instead of a method like all the others suggested?

Zepplock Over a year ago

Class is reusable and more readable, other solutions will lead to copy-paste (eventually).

Ransom Briggs · Accepted Answer · 2011-07-22 21:15:02Z

2

validate :if_first_is_false_second_is_also
def if_first_is_false_second_is_also
  if self.first_field == false && self.second_field != false
    errors.add(:second_field, "your error message")
  end
end

Comments

apneadiving · Accepted Answer · 2011-07-22 15:42:38Z

1

I assume here that when first is true, it's always ok.

validate :check_booleans

def check_booleans
  if first == false
     errors[:base] << "wrong here" if second == true
  end
end

edited Jul 22, 2011 at 15:42

answered Jul 22, 2011 at 15:36

apneadiving

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1 Comment

Brett Bender Over a year ago

Validations do not check return values, you need to add errors to the object: self.errors.add(:second, "can't be false")

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