Explanation of methods for skipping callbacks in Rails

Question

I have Video and Playlist models. To boost the process of displaying a thumbnail for the Playlist - I've made a column named 'thumbnail'. I would like it to be updated anytime when playlist is updated (because there's a lot of such situations in different parts of my app), so I tried to use callback after_update:

Class Playlist < ApplicationRecord

  after_update :set_thumbnail


  def set_thumbnail
    video_thumbnail = Video.find(self.content[0]).thumbnail
    self.update(thumbnail: video_thumbnail)
  end
end

Of course I've got endless cycle.

Rails docs just list methods for skipping callbacks (e.g. decrement, decrement_counter , etc.), so I have no idea how to use them.

score 0 · Answer 1 · answered Mar 09 '18 at 10:25

0

after_commit callback is more suitable here. This will be run after changes are saved to database unlike after_update which execute callbacks before actual commit to database.

after_commit :set_thumbnail, on: [:update]

answered Mar 09 '18 at 10:25

Ashik Salman

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Still I would like to know about skipping callbacks. – a-ta-ta Mar 09 '18 at 11:59
[Check this SO question](https://stackoverflow.com/questions/632742/how-can-i-avoid-running-activerecord-callbacks) – Ashik Salman Mar 09 '18 at 12:15

score 0 · Answer 2 · answered Mar 09 '18 at 10:43

0

May be it is better to use before_save here?

Class Playlist < ApplicationRecord

  before_save :set_thumbnail, on: :update


  def set_thumbnail
    video_thumbnail = Video.find(self.content[0]).thumbnail
  end
end

answered Mar 09 '18 at 10:43

Vasilisa

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Unfortunately. it doesn't improve the situation: update when update when update... until 'stack level's too deep'. – a-ta-ta Mar 09 '18 at 11:56
@a-ta-ta, please, check my answer carefully. You don't need to use `self.update` here, just set an attribute – Vasilisa Mar 09 '18 at 14:47

Explanation of methods for skipping callbacks in Rails

2 Answers2