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Active Support Subscriber

ActiveSupport::Subscriber 是一個用來使用 ActiveSupport::Notifications 的物件。根據所提供的命名空間，訂閱者會將通知傳送給已註冊的物件。

例如，一個 Active Record 訂閱者會負責收集有關查詢的統計資料

module ActiveRecord
  class StatsSubscriber < ActiveSupport::Subscriber
    attach_to :active_record

    def sql(event)
      Statsd.timing("sql.#{event.payload[:name]}", event.duration)
    end
  end
end

在設定完成後，只要發佈 "sql.active_record" 通知，它就會將事件 (ActiveSupport::Notifications::Event) 傳送給 sql 方法。

我們也可以取下訂閱

ActiveRecord::StatsSubscriber.detach_from(:active_record)
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類別公開方法

attach_to(namespace, subscriber = new, notifier = ActiveSupport::Notifications, inherit_all: false)

將訂閱者附加到命名空間。

來源： 顯示 | 查看 GitHub

# File activesupport/lib/active_support/subscriber.rb, line 35
def attach_to(namespace, subscriber = new, notifier = ActiveSupport::Notifications, inherit_all: false)
  @namespace  = namespace
  @subscriber = subscriber
  @notifier   = notifier
  @inherit_all = inherit_all

  subscribers << subscriber

  # Add event subscribers for all existing methods on the class.
  fetch_public_methods(subscriber, inherit_all).each do |event|
    add_event_subscriber(event)
  end
end

detach_from(namespace, notifier = ActiveSupport::Notifications)

將訂閱者從命名空間取下。

來源： 顯示 | 查看 GitHub

# File activesupport/lib/active_support/subscriber.rb, line 50
def detach_from(namespace, notifier = ActiveSupport::Notifications)
  @namespace  = namespace
  @subscriber = find_attached_subscriber
  @notifier   = notifier

  return unless subscriber

  subscribers.delete(subscriber)

  # Remove event subscribers of all existing methods on the class.
  fetch_public_methods(subscriber, true).each do |event|
    remove_event_subscriber(event)
  end

  # Reset notifier so that event subscribers will not add for new methods added to the class.
  @notifier = nil
end

method_added(event)

為新增到類別的所有新方法加入事件訂閱者。

來源： 顯示 | 查看 GitHub

# File activesupport/lib/active_support/subscriber.rb, line 69
def method_added(event)
  super
  # Only public methods are added as subscribers, and only if a notifier
  # has been set up. This means that subscribers will only be set up for
  # classes that call #attach_to.
  if public_method_defined?(event) && notifier
    add_event_subscriber(event)
  end
end

new()

來源： 顯示 | 查看 GitHub

# File activesupport/lib/active_support/subscriber.rb, line 131
def initialize
  @patterns  = {}
  super
end

subscribers()

來源： 顯示 | 查看 GitHub

# File activesupport/lib/active_support/subscriber.rb, line 79
def subscribers
  @@subscribers ||= []
end

類別私人方法

add_event_subscriber(event)

來源： 顯示 | 查看 GitHub

# File activesupport/lib/active_support/subscriber.rb, line 86
def add_event_subscriber(event) # :doc:
  return if invalid_event?(event)

  pattern = prepare_pattern(event)

  # Don't add multiple subscribers (e.g. if methods are redefined).
  return if pattern_subscribed?(pattern)

  subscriber.patterns[pattern] = notifier.subscribe(pattern, subscriber)
end

remove_event_subscriber(event)

來源：顯示 | 在 GitHub 上

# File activesupport/lib/active_support/subscriber.rb, line 97
def remove_event_subscriber(event) # :doc:
  return if invalid_event?(event)

  pattern = prepare_pattern(event)

  return unless pattern_subscribed?(pattern)

  notifier.unsubscribe(subscriber.patterns[pattern])
  subscriber.patterns.delete(pattern)
end

執行個體公開方法

call(event)

來源：顯示 | 在 GitHub 上

# File activesupport/lib/active_support/subscriber.rb, line 136
def call(event)
  method = event.name[0, event.name.index(".")]
  send(method, event)
end