How Active Record validation check, if type is array?

Question

I have attribute user`s languages. When form submit, it must return array?

I want to write validation in model User:

validates :languages, presence: true

How write in validates, returning value must be is array?

Are you saving this field? How is languages defined in the database? — Pablo
– Pablo, Commented Feb 7, 2018 at 2:23
in migration add_column :users, :languages, :string, array: true, default: [], strong parameters: params.require(:user).permit(:email, :password, :password_confirmation, languages: []) — Stefan Hansch
– Stefan Hansch, Commented Feb 7, 2018 at 2:36

Pablo · Accepted Answer · 2020-06-17 20:46:48Z

3

class User< ApplicationRecord
  validate :languages_is_array

  def languages_is_array
    if !languages.kind_of?(Array)
      errors.add(:languages, "must be an array")
    end
  end

  #Another version, as moveson commented
  def languages_is_array
    errors.add(:languages, "must be an array") unless languages.kind_of?(Array)
  end

end

edited Jun 17, 2020 at 20:46

answered Feb 7, 2018 at 3:02

Pablo

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1 Comment

moveson Over a year ago

Ruby idiom is to use unless instead of if followed by !. So in this case, unless languages.kind_of?(Array).

3limin4t0r · Accepted Answer · 2018-02-07 14:01:42Z

0

You can declare that a param needs to be an array in you controller if you are concerned about what the user submits in the form and not so much the validation of the model.

See: Action Controller Overview - 4.5 Strong Parameters

To declare that the value in params must be an array of permitted scalar values, map the key to an empty array:
params.permit(id: [])

answered Feb 7, 2018 at 14:01

3limin4t0r

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Comments

coalest · Accepted Answer · 2023-06-13 21:05:29Z

0

You can also create your own custom validator for attributes.

In this case it could look like:

class ArrayValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    unless value.is_a? Array
      record.errors.add attribute, (options[:message] || "must be an array")
    end
  end
end

class User < ApplicationRecord
  validates :languages, array: true
end

See: https://guides.rubyonrails.org/active_record_validations.html#custom-validators

answered Jun 13, 2023 at 21:05

coalest

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