Application layout not applied to form - ruby-on-rails

Question

In app/controllers/fw_exports_controller.rb, I have:
def import_spreadsheet
#followeds = Followed.all.order(:screen_name)
#import_spreadsheet = FwExport.new
render partial: 'fw_exports/import_spreadsheet'
end
In app/views/layouts/application.html.slim, I have:
doctype html
html
head
meta content=("text/html; charset=UTF-8") http-equiv="Content-Type" /
meta content="width=device-width, initial-scale=1.0" name="viewport" /
title= content_for?(:title) ? yield(:title) : t('project_name')
meta content=("#{content_for?(:description) ? yield(:description) : t('project_name')}") name="description" /
= stylesheet_link_tag 'application', media: 'all', 'data-turbolinks-track' => true
= javascript_include_tag 'application', 'data-turbolinks-track' => true
= csrf_meta_tags
body
header
= render 'layouts/navigation'
main role="main"
= render 'layouts/messages'
= yield
= render "layouts/footer"
In app/views/layouts/_navigation.html.slim, I have:
nav.navbar.navbar-default role="navigation"
.container
.navbar-header
a.navbar-brand href="#"
= t('parnassus_tools_home')
.navbar-left
ul.nav.navbar-nav
li
a
= link_to t('menus.upload_file'), import_spreadsheet_path
In app/views/fw_exports/_import_spreadsheet.html.slim, I have:
.container
h1
= t('fw_exports.choose_file_to_upload')
= form_tag process_imported_spreadsheet_path, html: { multipart: true }
.form-group
= file_field_tag :import_file
- if !#followeds[0].nil?
.form-group
= select_tag "followed_id", options_from_collection_for_select(#followeds, "id", "screen_name", "1")
.form_group
.sr-only
= label_tag t('fw_exports.screen_name_to_add')
= text_field_tag :screen_name_addition, placeholder: t('fw_exports.screen_name_to_add')
= button_tag(type: 'submit', class: "btn btn-primary") do
i.icon-ok.icon-white
= t('fw_exports.import')
In app/views/landings/index.html.slim, I have (this is the home page):
h1 Home Page
p test text
Here's what I see when I am on the home page:
But when I click on the Upload File menu item, from the home page, here's what I see:
Why isn't the application layout applied to the form?

Answer 1

You will need to render as a template and not as a partial. First, create a view template:
app/views/fw_spreadsheet/import_spreadsheet.html.slim
= render 'fw_exports/import_spreadsheet_form'
Next, rename your partial by changing the name of app/views/fw_spreadsheet/_import_spreadsheet.html.slim to app/views/fw_spreadsheet/_import_spreadsheet_form.html.slim
Finally, modify your controller as follows:
app/controllers/fw_exports_controller.rb
def import_spreadsheet
#followeds = Followed.all.order(:screen_name)
#import_spreadsheet = FwExport.new
render 'fw_exports/import_spreadsheet'
end