gistfile1.erb

<h1>Add Activity</h1>

<%= form_for @activity do |f| %>
  <%= f.label :name, "Activity Name" %></br>
  <%= f.text_field :name %></br>
  <%= f.label :address_one, "Address 1" %></br>
  <%= f.text_field :address_one %></br>
  <%= f.label :address_two, "Address 2" %></br>
  <%= f.text_field :address_two %></br>
  <%= f.label :city, "City" %></br>
  <%= f.text_field :city %></br>
  <%= f.label :state, "State" %></br>
  <%= f.text_field :state %></br>
  <%= f.label :zip_code, "Zip Code" %></br>
  <%= f.text_field :zip_code %></br>
  <%= f.label :description, "Description" %></br>
  <%= f.text_area :description %></br>
  <%= render partial: "shared/categories" %></br>

  <% Category.all.each do |category| %>
     <label>
        <%= check_box_tag "activity[category_ids][]", category.id, @activity.categories.include?(category) %>
        <%= category.category_name %></br>
     </label>
  <% end %>

  <%= f.submit %>
<% end %>