ruby 36 lines · 8 steps

Live-updating comments with Turbo in Rails

A Comment model pushes its own creates, updates, and deletes to subscribers over Turbo Streams.

Explained by highlit

Rails Intermediate turbo-streams callbacks associations real-time broadcasting

1class Comment < ApplicationRecord
belongs_to :post
belongs_to :author, class_name: "User"
4 
validates :body, presence: true, length: { maximum: 2_000 }
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scope :recent, -> { order(created_at: :desc) }
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after_create_commit :broadcast_creation
after_update_commit :broadcast_replacement
after_destroy_commit :broadcast_removal
12 
private
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def broadcast_creation
  broadcast_prepend_later_to(
    [post, :comments],
    target: dom_id(post, :comments),
    partial: "comments/comment",
    locals: { comment: self }
  )
  broadcast_update_later_to(
    [post, :comments],
    target: dom_id(post, :comments_count),
    html: post.comments.count
  )
end
28 
def broadcast_replacement
  broadcast_replace_later_to([post, :comments], target: self)
end
32 
def broadcast_removal
  broadcast_remove_to([post, :comments], target: self)
end
36end

01 / 01

STEP 01

Walkthrough

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Three takeaways

1Commit-time callbacks fire only after the transaction succeeds, so broadcasts never reference uncommitted data.
2Streaming to a shared `[post, :comments]` stream lets every subscriber receive the same DOM updates.
3Targeting elements by `dom_id` keeps server-rendered partials and client DOM in sync without custom JavaScript.

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