validates array elements inclusion using inclusion: { in: array }

Question

I use acts-as-taggable-on gem to populate a user interests on a User model like this

# User.rb
acts_as_taggable
acts_as_taggable_on :interests

As I populate the interest_list array, I need to check that the given values matches against a constant array to make sure these are accepted values, something like this

VALID_INTERESTS = ["music","biking","hike"]
validates :interest_list, :inclusion => { :in => VALID_INTERESTS, :message => "%{value} is not a valid interest" }

The code above returns the following error

@user = User.new
@user.interest_list = ["music","biking"]
@user.save
=> false …. @messages={:interest_list=>["music, biking is not a valid interest"]}

I can see the inclusion doesn't realize it should iterate over the array elements instead of s considering as a plain string but I'm not sure how to achieve this. Any idea?

This has been changed in Rails to work as you described it: github.com/rails/rails/commit/… The answers below should no longer be necessary in most cases. — dleavitt
– dleavitt, Commented Sep 26, 2022 at 23:53

Chris Salzberg · Accepted Answer · 2012-11-27 08:17:27Z

13

The standard inclusion validator will not work for this use case, since it checks that the attribute in question is a member of a given array. What you want is to check that every element of an array (the attribute) is a member of a given array.

To do this you could create a custom validator, something like this:

VALID_INTERESTS = ["music","biking","hike"]
validate :validate_interests

private

def validate_interests
  if (invalid_interests = (interest_list - VALID_INTERESTS))
    invalid_interests.each do |interest|
      errors.add(:interest_list, interest + " is not a valid interest")
    end
  end
end

I'm getting the elements of interest_list not in VALID_INTERESTS by taking the difference of these two arrays.

I haven't actually tried this code so can't guarantee it will work, but the solution I think will look something like this.

edited Nov 27, 2012 at 8:17

answered Nov 27, 2012 at 7:55

Chris Salzberg

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1 Comment

Ev Dolzhenko Over a year ago

This is a quite common pattern, surprising I wasn't able to find (quickly) the gem to do this.

webmaster-patche · Accepted Answer · 2018-12-20 04:55:55Z

0

It's a nice implementation, but I forget about one in the description of the model.

serialize : interest_list, Array

answered Dec 20, 2018 at 4:55

webmaster-patche

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1 Comment

Ankur Aggarwal Over a year ago

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mikeoleynik · Accepted Answer · 2019-11-29 08:38:07Z

0

You can implement your own ArrayInclusionValidator:

# app/validators/array_inclusion_validator.rb
class ArrayInclusionValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    # your code here

    record.errors.add(attribute, "#{attribute_name} is not included in the list")
  end
end

In the model it looks like this:

# app/models/model.rb
class YourModel < ApplicationRecord
  ALLOWED_TYPES = %w[one two three]
  validates :type_of_anything, array_inclusion: { in: ALLOWED_TYPES }
end

Examples can be found here:

edited Nov 29, 2019 at 8:38

answered Nov 29, 2019 at 8:30

mikeoleynik

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