parse_request_params error

In order to use swagger more convenient, I rewrite some attrs in Grape::Router::Route. And there is a problem when parsing the request params in the following code, for I add a Symbol type param behind an Array type param.

# lib/grape-swagger/endpoint.rb
def parse_request_params(params)
  array_key = nil
  params.select { |param| public_parameter?(param) }.each_with_object({}) do |param, memo|
    name, options = *param
    param_type = options[:type]
    param_type = param_type.to_s unless param_type.nil?
    array_key = name.to_s if param_type_is_array?(param_type)
    options[:is_array] = true if array_key && name.start_with?(array_key)
    memo[name] = options unless %w[Hash Array].include?(param_type) && !options.key?(:documentation)
  end
end

So is it better to to delete array_key = nil to set array_key a local variable in the block.

And there is another doubt for me. Why do you set array_key = name.to_s and then judge whether name.start_with?(array_key)? Why not directly use options[:is_array] = true if param_type_is_array?(param_type)?

Start in lib/grape-swagger/endpoint.rb at parse_request_params and reproduce the reported case with a Symbol parameter after an Array parameter. Trace array_key, param_type_is_array?, and public_parameter? to establish the intended array marking; done when the parsing error is resolved and the resulting parameter metadata matches the expected behavior.