Syntax Error: Unexpected '(', expecting '}' - ruby-on-rails

Question

I am having some trouble with my new public/private topic methods. I need to be able to apply a publicly_viewable method to my topics scope. However, I keep getting the following error:
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
I have also defined the publicly_viewable method within my topic model:
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
Topics Controller:
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
I am still quite new to scopes so anytime will be greatly appreciated.