Rails - Validation :if one condition is true

Question

On Rails 5.

I have an Order model with a description attribute. I only want to validate it's presence if one of two conditions is met: if the current step is equal to the first step OR if require_validation is equal to true.

I can easily validate based on one condition like this:

validates :description, presence: true, if: :first_step?

def first_step?
 current_step == steps.first
end

but I am not sure how to go about adding another condition and validating if one or the other is true.

something like:

validates :description, presence: true, if: :first_step? || :require_validation

Thanks!

SteveTurczyn · Accepted Answer · 2017-02-27 20:36:47Z

79

You can use a lambda for the if: clause and do an or condition.

validates :description, presence: true, if: -> {current_step == steps.first || require_validation}

answered Feb 27, 2017 at 20:36

SteveTurczyn

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1 Comment

Victor Cordeiro Costa Over a year ago

Beautiful solution.

jaredready · Accepted Answer · 2017-02-27 20:33:01Z

17

Can you just wrap it in one method? According to the docs

:if - Specifies a method, proc or string to call to determine if the validation should occur (e.g. if: :allow_validation, or if: Proc.new { |user| user.signup_step > 2 }). The method, proc or string should return or evaluate to a true or false value.

validates :description, presence: true, if: :some_validation_check

def some_validation_check
    first_step? || require_validation
end

answered Feb 27, 2017 at 20:33

jaredready

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Comments

Sebastián Palma · Accepted Answer · 2018-07-16 17:44:41Z

3

You can pass a lambda to be evaluated as the if condition.

Try:

validates :description, presence: true, if: -> { first_step? || require_validation }

edited Jul 16, 2018 at 17:44

Sebastián Palma

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answered Feb 27, 2017 at 20:38

Malav Bhavsar

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3 Comments

Brendon Muir Over a year ago

Isn't that a lambda? A block would be: validates :description, presence: true, if: { first_step? || require_validation }

Malav Bhavsar Over a year ago

Ah, you are right. I should have said "You can pass a lambda".

Brendon Muir Over a year ago

:) A block also works though. Rails just converts it to a proc or lambda (I forget what) before using it.

Alexander Kuznetsov · Accepted Answer · 2017-02-27 20:36:54Z

1

If you don't want to add one method as Jared say then you can try use lambda

validates :description, presence: true, if: ->{ first_step? || require_validation }

answered Feb 27, 2017 at 20:36

Alexander Kuznetsov

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Comments

Murat · Accepted Answer · 2019-11-11 18:19:06Z

1

If you have a lot case , you can design for validates

validates_presence_of :price_tech_fee, if: :price_tech_fee_require?, :message => :required

validates_presence_of :percentage_tech_fee, if: :percentage_tech_fee_require?, :message => :required

def percentage_tech_fee_require?
    is_active? && is_transaction_percentage? && is_premium?
  end

def is_active?
  !self.is_deleted && self.is_active
end

def is_transaction_percentage?
 self.is_per_transaction && self.is_percentage
end

def is_premium?
  ....
end

edited Nov 11, 2019 at 18:19

answered Nov 11, 2019 at 18:12

Murat

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1 Comment

Rorrim Over a year ago

Convention says that you shouldn't define a method that is called "is_,,," if it should return a boolean value. Just use "?" at the end (like you did).

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