ruby-on-rails - 使用服务类中的计算属性构建哈希

Question

我想帮忙完成一段代码。我不知道如何解释我需要什么，所以我会一点一点地告诉你。

我有这个模型:

class Metric < ApplicationRecord
  belongs_to: :post
  after_save: :analysis!

  # The table Metrics has the following columns:
  # adverb_count
  # adverb_density
  # sentiment
  # word_count
  # letter_count

  def analysis!
    res = MetricService.call post.body
    update! res
  end
end

保存度量实例后，我需要调用一个外部服务，该服务将返回一个哈希值，其中包含可帮助我计算值的属性adverb_count、adverb_density、sentiment，word_count，最后是 letter_count。为此，我创建了一个封装此逻辑的 MetricService 类:

class ApplicationService
  def self.call(*args, &block)
    new(*args, &block).call
  end
end

class MetricService < ApplicationService
  extend Memoist

  def initiaze(text)
    @text = text
  end

  # TODO: return the
  def call
    pre_analysis
    # =>
    #  Hash containing several props

    post_nalysis
    # =>
    #  Hash containing sereral props
  end

  private

  def pre_analysis
    client.pre_analysis @text
  end
  memoize :pre_analysis

  def post_analysis
    client.post_analysis pre_analysis['id']
  end

  def client
    SDK::Service.new ENV['API_KEY']
  end
  memoize :client
end

在这个类实例化之后，我调用了client的两个方法:pre_analysis和post_analyis，通过这两个信息我可以最后计算属性 adverb_count、adverb_density、sentiment、word_count 和 letter_count 的值并将其返回给 Metric。我想做的是为每个属性创建一个方法:

class MetricService < ApplicationService

   # ...
   def adverb_count
     # use pre_analysis and post_analysis to computate this value here
   end

   def adverb_density
     # use pre_analysis and post_analysis to computate this value here
   end

   def sentiment
     # use pre_analysis and post_analysis to computate this value here
   end

   def word_count
     # use pre_analysis and post_analysis to computate this value here
   end

   def letter_count
     # use pre_analysis and post_analysis to computate this value here
   end
   # ...
end

在 call 方法中，我只是调用它们并返回哈希值。

根据我的研究，ROR 上的服务应该只包含一个公共(public)方法，所以我想我应该将这些属性保密。这是一个正确的假设吗？

有没有一种方法可以从 #call 构建散列，而不必单独调用这些方法中的每一个？例如:

def call
  {
    adverb_count: adverb_count
    # etc
  }
end

谢谢。

Answer 1

您可以像这样使用元编程:

# the only public method
def call
  %w[adverb_count adverb_density sentiment word_count letter_count].each_with_object({}) do |method_name, result|
    result[method_name] = send(method_name)
  end
end

private

def adverb_count
  # use pre_analysis and post_analysis to computate this value here
end

def adverb_density
  # use pre_analysis and post_analysis to computate this value here
end

# and so on...