class ActionController::Parameters

def transform_values

# => #2, "b"=>4, "c"=>6} permitted: false>
params.transform_values { |x| x * 2 }
params = ActionController::Parameters.new(a: 1, b: 2, c: 3)

running +block+ once for every value. The keys are unchanged.
Returns a new +ActionController::Parameters+ instance with the results of 
def transform_values
  return to_enum(:transform_values) unless block_given?
  new_instance_with_inherited_permitted_status(
    @parameters.transform_values { |v| yield convert_value_to_parameters(v) }
  )
end