combined.rb

class CombinedFilter
  
  def initialize *klasses, params = {} # nicht sicher ob das funktioniert.
    @klasses = klasses
    @filters = @klasses.map do |klass|
      klass.new(params.slice(klass.class.attributes))
    end
  end
  
  def to_api_hash
    @filters.inject ...
  end
end

class Controller
  def index
    @filter = CombinedFilter.new(FirstFilter, SecondFilter, params[:filter])
  end
end