Rails 5: Adding conditional custom validations

Question

I would like to add a conditional custom validation to a model

Rails allows to create methods in order to create custom validations

class Invoice < ApplicationRecord
  validate :expiration_date_cannot_be_in_the_past

  def expiration_date_cannot_be_in_the_past
    if expiration_date.present? && expiration_date < Date.today
      errors.add(:expiration_date, "can't be in the past")
  end
end

It also allows to create conditional validations

class Order < ApplicationRecord
  validates :card_number, presence: true, if: :paid_with_card?

  def paid_with_card?
    payment_type == "card"
  end
end

How can I mix both ?

My guess would be something like

validate :condition, if: :other_condition

But this creates a SyntaxError:

syntax error, unexpected end-of-input, expecting keyword_end

Solution 1

When you fix the missing closing end to opened if in expiration_date_cannot_be_in_the_past, you can have the following working:

validate :expiration_date_cannot_be_in_the_past, if: :paid_with_card?

Solution 2

You can use each validator. For this you have to follow these steps:

• Create a folder named validators inside your app directory.
• Create a file named some_validator.rb

• Write codes as like:

  class SomeValidator < ActiveModel::EachValidator
   def validate_each(object, attribute, value)
     return unless value.present?
     if some_condition1
       object.errors[attribute] << 'error msg for condition1'
     end
    object.errors[attribute] << 'error msg 2' if condition2
    object.errors[attribute] << 'error msg 3' if condition3
    object.errors[attribute] << 'error msg 4' if condition4
  end
  

  end

• Now validates by this custom validator, as like: validates :attribute_name, some: true

• Make sure your are giving the same name on validator. You can write the multiple conditions inside this custom validator.

Solution 3

You missed end, corrected code:

class Invoice < ApplicationRecord
  validate :expiration_date_cannot_be_in_the_past

  def expiration_date_cannot_be_in_the_past
    if expiration_date.present? && expiration_date < Date.today
      errors.add(:expiration_date, "can't be in the past")
    end # this end you missed in code
  end
end

Solution 4

class User < ApplicationRecord
  validate :email_not_changeable, on: :update

  private

  def email_not_changeable
    return unless email_changed? && persisted?

    errors.add(:email, "can't be changed")
  end
end

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Comments

[craigcaulfield]

Code is always good, but it also helps to add some comments or context about how this solves the original question.

[Greenstick]

Echoing @craigcaulfield; please add some comments around how this solves the original question.