rails has_many minimum collection size update validation

Question

I have a has_many association that accepts nested attributes. I need for there to be a minimum of 1 associated object in the collection, so I wrote a custom va

Answer 1

Create validator:

class CollectionLengthValidator < ActiveModel::Validations::LengthValidator
  def validate_each(record, attribute, value)
    value = value.respond_to?(:reject) ? value.reject(&:marked_for_destruction?) : value
    super(record, attribute, value)
  end
end

This is resolve problem with delete last record in collection.

Then use in model as standard length validator:

validates :foos, :collection_length => {:minimum => 1}