在ruby??onrails應用程式中重用模型

我目前正在為我的一個模型添加評論，MaintenanceRequest并想知道我應該如何處理。

我有一個Offer已經建立了評論的模型，它是用 ActionCable 設定的，如下所示

# models/comment.rb

class Comment < ApplicationRecord
  belongs_to :user
  belongs_to :offer
end

# channels/comment_channel.rb

class CommentChannel < ApplicationCable::Channel
  def subscribed
    offer = Offer.find params[:offer]
    stream_for offer
  end
end

并且評論控制器看起來像

# controllers/comments_controller.rb

class CommentsController < ApplicationController
  before_action :authenticate_user!
  before_action :is_valid_offer

  def create
    offer = Offer.find(comment_params[:offer_id])

    if comment_params[:content].blank?
      # return redirect_to request.referrer, alert: 'Comment cannot be empty.'
      return render json: {success: false}
    end

    if offer.user_id != current_user.id && offer.landlord_id != current_user.id
      return render json: {success: false}
    end

    @comment = Comment.new(
      user_id: current_user.id,
      offer_id: offer.id,
      content: comment_params[:content],
    )

    if @comment.save
      # redirect_to request.referrer, notice: 'Comment sent.'
      CommentChannel.broadcast_to offer, message: render_comment(@comment)
      render json: {success: true}
    else
      redirect_to request.referrer, alert: "Couldn't send comment."
      render json: {success: true}
    end
  end
end

我的問題是，有沒有一種方法可以將相同的模型用于屬于評論的模型，MaintenanceRequest還是應該為評論創建新模型和控制器？如果我嘗試重用當前的評論模型，這似乎會變得非常混亂。這里的“最佳實踐”是什么？

uj5u.com熱心網友回復：

如果要創建可重用關聯，則要使用多型關聯：

class Comment < ApplicationRecord
  belongs_to :user
  belongs_to :commentable, 
    polymorphic: true

  validates :content, 
    presence: true
end

不是使用包含指向固定表的整數的單個列，而是通過使用一列作為其他表的主鍵并將物體的類名存盤在字串列中（在本例中稱為commentable_type）。

您可以通過在生成遷移（或模型）時傳遞多型選項來創建所需的列：

rails g migration add_commentable_to_comments commentable:belongs_to{polymorphic}

然而，控制器的動作有點像火車失事。它應該看起來更像這樣：

class CommentsController < ApplicationController
  before_action :authenticate_user!
  before_action :set_offer
  before_action :authorize_user

  def create
    @comment = @offer.comments.new(comment_params) do |c|
      c.user = current_user
    end

    if @comment.save
      # redirect_to request.referrer, notice: 'Comment sent.'
      CommentChannel.broadcast_to offer, message: render_comment(@comment)
      # rendering json here is actually just stupid. Just use a HTTP status code 
      # as a response if you're not actually returning the rendered entity.
      render json: { success: true }, 
        status: :created,
        location: @comment
    else
      # either return JSON which is actually useful or just a status code
      render json: { success: false }, 
        status: :unprocessable_entity
    end
  end

  private

  def set_offer
    @offer = Offer.find(params[:offer_id])
  end

  # this should be extracted to an authorization layer such as Pundit
  def authorize_offer
    if @offer.user_id != current_user.id && @offer.landlord_id != current_user.id 
      render json: { success: false },
        status: :unauthorized
    end
  end
end

有兩種方法可以將此控制器重用于不同型別的“評論”。您可以檢查單個控制器中是否存在offer_id或maintenance_request_id并使用它來推斷類，或者您可以使用繼承來更好地分配職責：

# routes.rb

resources :offers do
  resources :comments, 
    only: :create,
    module: :offers
end

resources :maintainence_requests do
  resources :comments, 
    only: :create,
    module: :maintainence_requests
end

class CommentsController
  before_action :set_commentable, only: [:new, :create, :index]
  before_action :authenticate_user!
  attr_reader :commentable

  def create
    @comment = commentable.comments.new(comment_params) do |c|
      c.user = current_user
    end
    if @comment.save
      # simple extendability feature that lets you "tap into" the flow 
      # by passing a block when calling super in subclasses
      yield @comment if block_given?
      render json: @comment,
             status: :created
    else
      render json: { errors: @comment.errors.full_messages },
             status: :unprocessable_entity
    end
  end

  
  private

  # Uses simple heuristics based on module nesting to guess the name of the model
  # that is being commented upon. Overide if needed.
  # @example Foos::BarsController -> Foo
  def commentable_class
    @commentable_class ||= self.class.module_parent.name.singularize.constantize
  end 

  def commentable_param_key
    commentable_class.model_name.param_key
  end

  def set_commentable
    @commentable = commentable_class.find("#{commentable_param_key}_id")
  end

  def comment_params
    params.require(:comment)
          .permit(:content)
  end
end

module Offers
  class CommentsController < ::CommentsController
    # POST /offers/:offer_id/comments
    def create
      # block is called after a comment is succesfully saved but before 
      # the response is set
      super do |comment|
        CommentChannel.broadcast_to comment.offer, 
          message: render_comment(comment) 
      end
    end
  end
end

module MaintainenceRequests
  class CommentsController < ::CommentsController
  end
end

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