Custom predicates for Ransack, allows you to search inside a YAML-serialized Array column

demo.rb

# some model
serialize :my_field, Array

ransacker :my_field_raw, type: :string do
  Arel.sql('my_table.my_field')
end


# some view (using simple form)
= search_form_for @q, builder: SimpleForm::FormBuilder do |f|
  = f.input :my_field_raw_yaml_array_matches_all, collection: [...], input_html: { multiple: true }

ransack.rb

# config/initializers/ransack.rb

def arrayable?(value)
  value.present? && (value.is_a?(Array) || JSON.parse(value).is_a?(Array))
rescue
  false
end

def to_array(value)
  return value if value.is_a?(Array)
  JSON.parse(value)
end

Ransack.configure do |config|
  config.add_predicate 'yaml_array_matches_all',
    arel_predicate: 'matches_all',
    formatter: proc { |value|
      to_array(value).map do |v|
        "%- '#{v.strip}'\n%"
      end
    },
    validator: proc { |value| arrayable?(value) },
    type: :string

  config.add_predicate 'yaml_array_does_not_match_any',
    arel_predicate: 'does_not_match_any',
    formatter: proc { |value|
      to_array(value).map do |v|
        "%- '#{v.strip}'\n%"
      end
    },
    validator: proc { |value| arrayable?(value) },
    type: :string
end