How do I validate that two values do not equal each other in a Rails model?

I have a User model, wh开发者_开发知识库ich has an email and a password field. For security, these may not be equal to each other. How can I define this in my model?

---

Create custom validataion:

validate :check_email_and_password

def check_email_and_password
  errors.add(:password, "can't be the same as email") if email == password
end

But keep in mind that storing password as a plain text is bad idea. You should store it hashed. Try some authentication plugin like authlogic or Restful authentication.

---

New way:

validates :password, exclusion: { in: lambda{ |user| [user.email] } }

or:

validates :password, exclusion: { in: ->(user) { [user.email] } }

---

You can use a custom validation method to check this.

class User < ActiveRecord::Base
  # ...

  def validate
    if (self.email == self.password)
      errors.add(:password, "password cannot equal email")
      errors.add(:email, "email cannot equal password")
    end
  end
end

---

It depends how Your password is stored:

class User < ActiveRecord::Base
    validate :email_and_password_validation

    def email_and_password_validation
        if self.email == self.password
            errors.add_to_base("Password must be different from email") 
        end
    end
end

This would work if Your password is stored literally, but You can perform the same thing with email (e.g. create a hashed version) and check for equality with password. E.g:

class User < ActiveRecord::Base
    validate :email_and_password_validation

    def email_and_password_validation
        if make_hash(self.email) == self.hashed_password
            errors.add_to_base("Password must be different from email") 
        end
    end
end

My example is taken from http://api.rubyonrails.org/classes/ActiveRecord/Validations/ClassMethods.html#M002162

Your situation is quite general so You can be interested in creating custom validation method. Everything is covered here: http://guides.rubyonrails.org/active_record_validations_callbacks.html#creating-custom-validation-methods

---

it is much wiser to use custom validator, here is code for universal validator that can be used

class ValuesNotEqualValidator < ActiveModel::Validator
  def validate(record)
    if options[:fields].any? && options[:fields].size >= 2
      field_values = options[:fields].collect { |f| record.send(f) }
      unless field_values.size == field_values.uniq.size
        record.errors[:base] <<
            (options[:msg].blank? ? "fields: #{options[:fields].join(", ")} - should not be equal" :
                options[:msg])
      end
    else
      raise "#{self.class.name} require at least two fields as options [e.g. fields: [:giver_id, :receiver_id]"
    end
  end
end

and then use it like:

class User < ActiveRecord::Base
  # ...
  validates_with ValuesNotEqualValidator, fields: [:email, :password], msg: "This Person is evil"
end

---

more fun:

  validates :password, exclusion: { in: ->(person) { [person.email] }, message: "cannot use protected password" }

which might be even better in this case, since you could check for other forbidden values with something like

  validates :password, exclusion: { in: ->(person) { [person.email, person.first_name, person.last_name, person.phone_number, person.department_name] }, message: "cannot use protected password" }

---

Ruby on Rails 7.0 added support for validates_comparison_of validations like this

validates :password, comparison: { other_than: :email }

---

all you need is to create validation rule in your model for example

class User < ActiveRecord::Base
  def validate_on_create
    if email == password
      errors.add("password", "email and password can't be the same")
    end
  end
end

---

If you want to support multiple languages, you have to come up with another solution, which translates the error messages and the attribute names. So I created a new each validator for that.

validators/values_not_equal_validator.rb:

class ValuesNotEqualValidator < ActiveModel::EachValidator
  def validate(record)
    @past = Hash.new
    super
  end

  def validate_each(record, attribute, value)
    @past.each do |k, v|
      if v == value
        record.errors.add(attribute, I18n.t('errors.messages.should_not_be_equal_to') + " " + record.class.human_attribute_name(k))
      end
    end
    @past[attribute] = value
  end
end

I call it in the model like this:

class User < ActiveRecord::Base
  validates :forename, :surname, values_not_equal: true
end

And I translate it the messages like this:

de:
  activerecord:
    attributes:
      user:
        forename: 'Vorname'
        surname: 'Nachname'
  errors:
    messages:
      should_not_be_equal_to: 'darf nicht gleich sein wie'

---

By using custom validations we can do this operation

validate :validate_address

def validate_address
errors.add(:permenent_address, "can't be the same as present_address") if self.present_address== self.permenent_address end