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?

Answer 1

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.