3

Lets say I have the following model:

class Car < ActiveRecord::Base

attr_accessible :wheels,
                :engine_cylinders

validates :wheels, :engine_cylinders, presence: true, numericality: true

end

Lets say I then have the following controller action:

@car = Car.find(params[:id])
@car.wheels = "foo"
@car.engine_cylinders = 4
@car.save

This save will fail as wheels will fail the numericality condition.

Is there any way to persist the succesful attributes (in this case engine_cylinders), while adding the invalid attributes to the errors array? E.g. is there a "soft" validation in Rails?

Improve this question
2
  • This really should be clarified (e.g. definition of "propogate"). Also, note that validations communicate with the save mechanism by populating the errors array, so any validation which adds something to that array is going to prohibit any subsequent save. Commented Sep 5, 2013 at 20:31
  • Though 'propagate to disk' is a common idea, "persist" is probably the more standard verbiage. Commented Sep 5, 2013 at 20:53

3 Answers 3

Reset to default
1

You want to write a Custom Validator.

class Car < ActiveRecord::Base
  validate :wheel_range,
           :engine_cylinder_range

  def engine_cylinder_range
    flash[:notice] = "engine_cylinder was not saved because it wasn't a number" unless engine_cylinder.is_a? Fixnum
    # set engine_cylinder back to old value
  end

  def wheel_range
    flash[:notice] = "wheels was not saved because it wasn't a number" unless wheels.is_a? Fixnum
    # set wheels back to old value
  end
end

You don't have to use flash here, you could use any variable for internal processing or re-display.

You may also want to put this custom validation check on the :before_save hook. Use the _was magic method to get the old value.

Improve this answer
Sign up to request clarification or add additional context in comments.

10 Comments

Custom validation methods should not raise, but do errors.add(:attr, ...). And most definitely they should not raise anything inheriting from Exception. Descendants of StandardError are app level errors and others inheriting from Exception are about environment. Also plain rescue without type won't catch the latter.
@TeroTilus I thought that adding errors would thus prevent the save, which OP wants to ensure occurs in all cases. So errors.add and then self.save ? Clearly we want this validation-handling to occur in the validator, else we will litter the code with log 'zzz' unless something.valid?; something.save(validate: false) which is just messy
It does prevent the save. So most definitely does raising an error. He should do @car.valid? when he wants to check the validity and @car.save(:validate => false) when he wants to save bypassing validations, as @pdobb already pointed out.
@TeroTilus Read the question again: OP wants to propagate attributes the are valid, and alert/warn/notify of the others without saving them
Do you read "propagate" to mean "save", because I interpreted it as "notify somebody". If you do, that together with your non-raising answer makes sense.
|
1

If you're looking to bypass validations you can always do so with:

if @car.save
  # ...
else
  @car.save(validate: false)
end

You may want to have a different conditional on that or whatever... but this is how you bypass validations on a one-off basis.

This may, however, destroy the errors array so you could rebuild it after the save(validate: false) with:

@car.valid?

You can also bypass validations one-at-a-time using @car.update_attribute(:attribute, <value>).

Improve this answer

Comments

0

If you just want to know if the model is valid or not without saving it @car.valid? does exactly that. It also adds invalid attributes to errors array. And @pdobb already pointed out how to bypass validation when saving.

Improve this answer

Comments

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.