在 Rails 应用程序控制器中缓存变量

Question

我在应用程序控制器中有以下代码：

class ApplicationController < ActionController::Base
  before_filter :find_today_forecast
  ...
  def find_today_forecast
    @today_forecast = Weather.displayed.city(@city).first
  end
end

变量@today_forecast 仅在我在生产和开发环境中重新启动应用程序时更新。

Rails.cache.clear 和 rake tmp:clear 不起作用。有什么问题

更新，天气模型和 YandexWeather 解析器：

class Weather < ActiveRecord::Base
  DISPLAY_COUNT = 7
  belongs_to :city
  scope :city, lambda {|field| {:conditions => {:city_id => field}}}

  validates_presence_of :temp_high, :temp_low
  validates_uniqueness_of :date, :scope => :city_id

  scope :displayed, :conditions => ['date >= ?', Date.today], :order => 'date ASC', :limit => Weather::DISPLAY_COUNT

  def high
    self.temp_high.to_i > 0 ? '+' + self.temp_high.to_s : self.temp_high
  end

  def low
    self.temp_low.to_i > 0 ? '+' + self.temp_low.to_s : self.temp_low
  end

  # загружаем погоду из Яндекса
  def self.load(city)
    begin
      YandexWeather.new(city).create_weathers
    rescue
      Rails.logger.info "no weather for city - #{city.title}"
    end
  end

end

class YandexWeather
  ICON_NAMES = {
    'ovc_ra' => 'heavy-rain',
    'ovc_-ra' => 'heavy-rain',
    'bkn_na' => 'heavy-cloud-day',
    'skc_n' => 'sun',
    'skc_d' => 'night',
    'ovc' => 'heavy-cloud-day',
    'bkn_-ra_n' => 'heavy-rain',
    'bkn_d' => 'medium-cloud',
    'bkn_n' => 'medium-cloud-night',
    'bkn_-ra_d' => 'rain',
    'ovc_-sn' => 'snow',
    'ovc_ts_ra' => 'heavy-storm',
    'bkn_-sn_n' => 'snow',
    'ovc_sn' => 'snow',
    'bkn_-sn_d' => 'chance_of_snow',
    'bkn_ra_d' => 'rain',
    'bkn_ra_n' => 'rain'
  }

  PER_PAGE = 10

  def initialize city
    @agent = Mechanize.new
    @city = city
  end

  ...
end

Answer 1

问题出在您的displayed 范围内

scope :displayed, :conditions => ['date >= ?', Date.today], :order => 'date ASC', :limit => Weather::DISPLAY_COUNT

Date.today 只在第一次被评估。

您需要将其更改为 lambda 范围，以便在每次调用时对其进行评估。

scope :displayed, -> {
  where("date >= ?", Date.today).
  order("date ASC").limit(Weather::DISPLAY_COUNT)
}

一般来说，只要您的作用域中有变化的部分，您就应该将其实现为 lambda (->) 作用域。