对参数结构进行重构，以通过 grape 的数组参数验证，并且与 Rails 的参数机制兼容

params_cleaner.rb

# 将参数 {associations_attributes: {"1" => {xxx: xxx}, "2" => {xxx: xxx}}} 中的 Hash 型参数转为数组型：
# =>
#   {
#     associations_attributes: [
#       {xxx: xxx},{xxx: xxx}
#     ]
#   }
#
# 满足 grape 中 type: Array[OtherTypeName]的验证
#
module Helpers
  module ParamsCleaner
    # 对参数结构进行重构，以通过 grape 的数组参数验证，并且与 Rails 的参数机制兼容
    #
    # 场景:
    # 1) 将类似 params[:message][:receiver_ids] => {"0"=>"72", "1"=>"82"} 清洗重构为 ["72", "82"]
    # 2) 将 params[:photo_album][:photo_album_allowed_visitors_attributes] =>
    #     {"1"=>{"allowed_visitor_id"=>"1", "allowed_visitor_type"=>"Klass"},
    #      "2"=>{"allowed_visitor_id"=>"2", "allowed_visitor_type"=>"Grade"}}
    #    清洗为：
    #     [{"allowed_visitor_id"=>"1", "allowed_visitor_type"=>"Klass"},
    #      {"allowed_visitor_id"=>"2", "allowed_visitor_type"=>"Grade"}]
    # 3) 清洗: params[:survey][:survey_questions_attributes][][:survey_answers_attributes][][:answer]
    #
    # 实例：
    # 转换前：
    #   {"survey"=>
    #     {"survey_invitations_attributes"=>
    #       {"1"=>{"invitee_id"=>"72", "invitee_type"=>"Klass"}, "2"=>{"invitee_id"=>"82", "invitee_type"=>"Klass"}},
    #      "survey_questions_attributes"=>
    #       {"1"=>
    #         {"question_type"=>"single_choice",
    #          "question"=>"您孩子的身高是？",
    #          "survey_answers_attributes"=>{"1"=>{"answer"=>"165"}, "2"=>{"answer"=>"175"}}},
    #        "2"=>
    #         {"question_type"=>"multiple_choices",
    #          "question"=>"喜欢的水果有？",
    #          "survey_answers_attributes"=>{"1"=>{"answer"=>"西瓜"}, "2"=>{"answer"=>"菠萝"}}}}}}
    #
    # 转换后：
    #   {"survey"=>
    #     {"survey_invitations_attributes"=>
    #       [{"invitee_id"=>"72", "invitee_type"=>"Klass"}, {"invitee_id"=>"82", "invitee_type"=>"Klass"}],
    #      "survey_questions_attributes"=>
    #       [{"question_type"=>"single_choice",
    #         "question"=>"您孩子的身高是？",
    #         "survey_answers_attributes"=>[{"answer"=>"165"}, {"answer"=>"175"}]},
    #        {"question_type"=>"multiple_choices",
    #         "question"=>"喜欢的水果有？",
    #         "survey_answers_attributes"=>[{"answer"=>"西瓜"}, {"answer"=>"菠萝"}]}]}}
    #
    def reconstruct_params
      params.each do |key, value|   # key: :message, value: {klass_ids: {xxx: xxx}}
        if value.is_a? Hash
          value.each do |sub_key, sub_value| # sub_key: :klass_ids, value: {"1"=> something, "2" => another_thing }
            # value 类似： params[:photo_album]
            if sub_value.is_a?(Hash)
              params[key][sub_key] = transform_params(sub_value)
            end
          end
        end
      end
    end

    def transform_params(nested_params)
      # 确保只对类如 {"1"=> something, "2" => another_thing } 这样的参数进行重构
      if nested_params.keys.all?{|key| is_numberical_integer?(key)}
        nested_params.values.map do |nested_param_value|
          # 对嵌套的参数进行进一步清洗
          # {"question_type"=>"single_choice",
          #  "question"=>"您孩子的身高是？",
          #  "survey_answers_attributes"=>
          #   {"1"=>{"answer"=>"165"},
          #    "2"=>{"answer"=>"175"}}}
          #
          if nested_param_value.is_a? Hash
            nested_param_value.each do |nested_key, nested_value|
              if nested_value.is_a? Hash
                nested_param_value[nested_key] = transform_params(nested_value)
              end
            end
          else
            nested_param_value
          end
        end
      else
        nested_params
      end
    end

    def is_numberical_integer?(value)
      # value 是一个纯数字的字符串, 或者本身就是一个整数
      value.is_a?(String) && value =~ /^\d+$/ || value.is_a?(Integer)
    end
  end
end