Upload doesn't work using Carrierwave in Rails 5 - ruby-on-rails

Question

So I was working on my app and trying to put on an uploader feature.
First I generated a course uploader and allowed jpeg, jpg, png and gif.
Next I've added the ff code mount on my course model:
mount_uploader :thumb_image, CoursesUploader
mount_uploader :main_image, CoursesUploader
Next, I place the file upload form code on my new.html.erb file:
<div class="field">
<%= f.file_field :main_image %>
</div>
<div class="field">
<%= f.file_field :thumb_image %>
</div>
And when I tried to submit my form with my images uploaded it did not even show the index page instead I refresh the page and then see if it got uploaded and the form was submitted successfully but it did not.
I also look at the strong params on my controller and these two items are there:
# Never trust parameters from the scary internet, only allow the white list through.
def course_params
params.require(:course).permit(:title, :price, :body, :main_image, :thumb_image)
end
Any idea what am I missing here?
Here's something I got from my terminal after submission:
Started POST "/courses" for 127.0.0.1 at 2019-01-16 20:52:20 +0800
Processing by CoursesController#create as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"wlKpv8czsuC6AZjCctxYk203wry4cb0dnOYI9IoAkzRZNV2vB4/vREU5L5u4G7vh5ZhCbHZlJ6nHPN95qO+cbA==", "course"=>{"title"=>"Goody", "price"=>"33", "main_image"=>#<ActionDispatch::Http::UploadedFile:0x007f81e52eed48 #tempfile=#<Tempfile:/var/folders/3_/8bmsd3j13bxfdl1jp7gzvvsm0000gn/T/RackMultipart20190116-2359-17w6pb.jpg>, #original_filename="61230.jpg", #content_type="image/jpeg", #headers="Content-Disposition: form-data; name=\"course[main_image]\"; filename=\"61230.jpg\"\r\nContent-Type: image/jpeg\r\n">, "thumb_image"=>#<ActionDispatch::Http::UploadedFile:0x007f81e52eecd0 #tempfile=#<Tempfile:/var/folders/3_/8bmsd3j13bxfdl1jp7gzvvsm0000gn/T/RackMultipart20190116-2359-2mcy4i.jpg>, #original_filename="61230.jpg", #content_type="image/jpeg", #headers="Content-Disposition: form-data; name=\"course[thumb_image]\"; filename=\"61230.jpg\"\r\nContent-Type: image/jpeg\r\n">, "body"=>""}, "commit"=>"Create Course"}
(0.5ms) BEGIN
↳ app/controllers/courses_controller.rb:27
Course Exists (1.5ms) SELECT 1 AS one FROM "courses" WHERE "courses"."id" IS NOT NULL AND "courses"."slug" = $1 LIMIT $2 [["slug", "goody"], ["LIMIT", 1]]
↳ app/controllers/courses_controller.rb:27
(0.6ms) ROLLBACK
↳ app/controllers/courses_controller.rb:27
Rendering courses/new.html.erb within layouts/application
Rendered courses/new.html.erb within layouts/application (12.6ms)
Rendered shared/_application_nav.html.erb (6.2ms)
Rendered shared/_application_footer.html.erb (1.3ms)
Completed 200 OK in 394ms (Views: 356.6ms | ActiveRecord: 2.6ms)
UPDATE: FULL MODEL CONTENT
class Course < ApplicationRecord
include DefaultsConcern
enum status: { draft: 0, published: 1 }
validates_presence_of :title, :price, :body, :main_image, :thumb_image
mount_uploader :thumb_image, CoursesUploader
mount_uploader :main_image, CoursesUploader
extend FriendlyId
friendly_id :title, use: :slugged
end
FULL FORM CONTENT:
<h1>New Form</h1>
<%= form_for(#course) do |f| %>
<div class="field">
<%= f.label :title %>
<%= f.text_field :title %>
</div>
<div class="field">
<%= f.label :price %>
<%= f.number_field :price %>
</div>
<div class="field">
<%= f.file_field :main_image %>
</div>
<div class="field">
<%= f.file_field :thumb_image %>
</div>
<div class="field">
<%= f.label :body %>
<%= f.text_area :body %>
</div>
<div class="actions">
<%= f.submit %>
</div>
<% end %>

Answer 1

Validation failed as params[:course][:body] is nil due to which creating course rolled back
validates_presence_of :title, :price, :body, :main_image, :thumb_image
=> So just fillup body field in form or remove validates_presence_of :body

Answer 2

I can see the Image is ActionDispatch already but are you sure you created your table column like this -Regardless of creating table or adding_column-
I'm focusing on
:string, array: true, default: []
Migration should look like:
add_column :courses, :main_image, :string, array: true, default: []
As creating the column as String won't let carrierwave add it's object as an array inside it, so it should be an array
Also you can set thumb and main images in one uploader if you are going to change the size only, otherwise you're fine to use :thumb_image and :main_image but make sure the migration is correct
If you can't change it, just drop and re-create it