add and remove collaborators solution

add_or_remove.html.erb

<!-- wiki_collaborations/add_or_remove.html.erb -->

<!-- how can this be cleaned up? -->
<div class="row">
  <div class="col-sm-6">
    <%= form_for wiki, url: wiki_collaborations_path, method: :post do %>
    <%= hidden_field_tag :wiki_id, wiki.id %>
  <% @users.each do |user| %>
    <% next if current_user == user %>
    <div class="checkbox">
    <%= check_box_tag "user_ids[]", user.id, wiki.users.include?(user) %>
    <%= user.username %>
    <% if wiki.users.include?(user) %>
      <% wiki.wiki_collaborations.each do |wiki_collaboration| %>
        <% if user.wiki_collaborations.include?(wiki_collaboration) %>
          <%= link_to "| Remove", wiki_collaboration, method: :delete %>
        <% end %>
      <% end %>
    <% end %>
  </div>
  <% end %>

  <%= submit_tag 'Add Collaborators', class: 'btn btn-primary' %>

  </div>

<% end %>
</div>

show.html.erb

<h1><%= @wiki.title %></h1>
<h4>Published by <%= @wiki.user.username %></h4>
<br>
<%= @wiki.body %>

<hr>

<% if user_signed_in? && @wiki.user == current_user %> <!-- more security needed? -->

<h1>Add Collaborators</h1>

<%= render template: 'wiki_collaborations/add_or_remove', locals: { wiki: @wiki } %>

<% end %>

wiki_collaborations_controller.rb

class WikiCollaborationsController < ApplicationController
before_filter :setup, only: [:create]  # Best way to accomplish this?
before_filter :authenticate_user!, only: [:create]

  def add_or_remove
  end

  ## TODO: If wiki already has some collaborations and no new values are selected, do not attempt
  ## a save and flash the correct notification
  ## TODO: Ajaxify
  def create
    @user_ids = params[:user_ids]
    @user_ids.each do |user_id| 
      next if @collaborator_ids.include?(user_id.to_i)
      @wiki_collaboration = @wiki.wiki_collaborations.new(wiki_id: @wiki, user_id: user_id)
      @wiki_collaboration.save
    end
    flash[:success] = "Collaborators added."
    redirect_to @wiki
  end

  ## TODO: Ajaxify

  def destroy
    @wiki_collaboration = WikiCollaboration.find(params[:id])
    if @wiki_collaboration.destroy
      flash[:notice] = "User removed."
      redirect_to :back
    end
  end

  private

  def setup
    @wiki = Wiki.find(params[:wiki_id]) # Should this be
                                        # @wiki = current_user.wikis.find(params[:wiki_id]) ?
    @wiki_collaborations = @wiki.wiki_collaborations
    @wiki_users = @wiki.users
    @collaborator_ids = []
    @wiki_users.each { |user| @collaborator_ids << user.id }
  end
end

wikis_controller.rb

class WikisController < ApplicationController
  before_filter :authenticate_user!, except: [:show]

  def new
    @wiki = current_user.wikis.new
  end

  def create
    @wiki = current_user.wikis.build(params[:wiki])
    if @wiki.save
      flash[:success] = "Wiki created!"
      redirect_to @wiki
    else
      render :new
    end
  end

  def show
    @users = User.all # Why do I have to list all users here
                      # and am unable to do so in 
                      # wiki_collaborations controller?
    @wiki = Wiki.find(params[:id])
  end