语法错误：意外＆＃39;（＆＃39;，期待＆＃39;}＆＃39;

Question

我在使用新的公共/私人主题方法时遇到了一些麻烦。我需要能够将public_viewable方法应用于我的主题范围。但是，我一直收到以下错误：

SyntaxError in TopicsController#index
/Users/ericpark/rails_projects/bloccit-2/app/models/topic.rb:7: syntax error, unexpected '(', expecting '}' scope :visible_to, -> { :publicly_viewable(user) } ^ /Users/ericpark/rails_projects/bloccit-2/app/models/topic.rb:20: syntax error, unexpected keyword_end, expecting '}'

Extracted source (around line #7):
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  validates :name, length: {minimum: 5}, presence: true

  scope :visible_to, -> { :publicly_viewable(user) }

  def publicly_viewable(user)
    if user

我还在我的主题模型中定义了public_viewable方法：

class Topic < ActiveRecord::Base
  has_many :posts, dependent: :destroy
  belongs_to :user

  validates :name, length: {minimum: 5}, presence: true

  scope :visible_to, -> { :publicly_viewable(user) }

  def publicly_viewable(user)
    if user
      topic_collection.all
    else
      topic_collection.where(public: true)
    end
  end

  def privately_viewable
    topic_collection.where(public: false)
  end
end

主题控制器：

class TopicsController < ApplicationController

  def index
    @topics = Topic.visible_to(current_user).paginate(page: params[:page], per_page: 10)
    authorize @topics
  end

  def show
    @topic = Topic.find(params[:id])
      @posts = @topic.posts.paginate(page:params[:page])
    authorize @topic
  end

  def new
    @topic = Topic.new
    authorize @topic
  end

  def edit
    @topic = Topic.find(params[:id])
     authorize @topic
  end

  def create
    @topic = Topic.new(topic_params)
     authorize @topic
     if @topic.save
       redirect_to @topic, notice: "Topic was saved successfully."
     else
       flash[:error] = "Error creating topic. Please try again."
       render :new
     end
  end

  def update
    @topic = Topic.find(params[:id])
     authorize @topic
     if @topic.update_attributes(topic_params)
       redirect_to @topic
     else
       flash[:error] = "Error saving topic. Please try again."
       render :edit
     end
  end

  def destroy
    @topic = Topic.find(params[:id])
    authorize @topic
    if @topic.destroy
      flash[:notice] = "\"#{@topic.name}\" was deleted successfully."
      redirect_to topics_path
    else
      flash[:error] = "There was an error deleting the topic."
      render :show
    end
  end

  private
  def topic_params
    params.require(:topic).permit(:name, :description, :public)
  end
end

我对范围仍然很新，所以任何时候都会非常感激。