CarrierWave not working - ruby-on-rails

Question

Ruby version 2.1.5 and rails 4.1.8.
So i am working on an app, using devise for authentication process. i need to add an avatar option where user can upload an image and for this i am using carrierwave. i follow all the instructions given here, but avatar is not saving anywhere.
here is my avatar_uploader.rb
class AvatarUploader < CarrierWave::Uploader::Base
storage :file
def store_dir
"public/uploads"
end
end
here is my model user.rb
class User < ActiveRecord::Base
mount_uploader :avatar, AvatarUploader
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable,
:validatable, :confirmable, :timeoutable
attr_accessor :login, :avatar, :avatar_cache, :remove_avatar
validates :username, presence: true, uniqueness: true
validate :email
def email_required?
false
end
def self.find_first_by_auth_conditions(warden_conditions)
conditions = warden_conditions.dup
if login = conditions.delete(:login)
where(conditions).where(["lower(username) = :value OR lower(email) = :value", { :value => login.downcase }]).first
else
where(conditions).first
end
end
end
here is my index.html.erb
<h2>Sign up</h2>
<%= form_for(resource, as: resource_name, url: registration_path(resource_name), :html => {:multipart => true}) do |f| %>
<%= devise_error_messages! %>
<div class="field">
<%= f.label :username %>
<% if Own_settings.minimum_username_length %>
<em>(<%= Own_settings.minimum_username_length %> characters minimum)</em>
<% end %><br />
<%= f.text_field :username, autofocus: true%>
</div>
<div class="field">
<%= f.label :email %>
<em>(Optional)</em><br />
<%= f.email_field :email %>
</div>
<div class="field">
<%= f.label :password %>
<% if #minimum_password_length %>
<em>(<%= #minimum_password_length %> characters minimum)</em>
<% end %><br />
<%= f.password_field :password, autocomplete: "off" %>
</div>
<div>
<%= f.file_field :avatar %><br />
<%= f.hidden_field :avatar_cache %><br />
</div>
<div class="actions">
<%= f.submit "Sign up" %>
</div>
<% end %>
<%= render "devise/shared/links" %>
here is my edit.html.erb
<h2>Edit <%= resource_name.to_s.humanize %></h2>
<%= form_for(resource, as: resource_name, url: registration_path(resource_name), html: { method: :put, multipart: :true }) do |f| %>
<%= devise_error_messages! %>
<div>
<% if current_user.avatar.url.present? %>
<%= image_tag current_user.avatar.url.to_s %>
<%= f.label :remove_avatar %>
<%= f.check_box :remove_avatar %>
<% end %>
<%= f.file_field :avatar %>
<%= f.hidden_field :avatar_cache %>
</div>
<div class="field">
<%= f.label :username %>
<% if Own_settings.minimum_username_length %>
<em>(<%= Own_settings.minimum_username_length %> characters minimum)</em>
<% end %><br />
<%= f.text_field :username, autofocus: true%>
</div>
<div class="field">
<%= f.label :email %><br />
<%= f.email_field :email, autofocus: true %>
</div>
<% if devise_mapping.confirmable? && resource.pending_reconfirmation? %>
<div>Currently waiting confirmation for: <%= resource.unconfirmed_email %>
<div/>
<% end %>
<div class="field">
<%= f.label :password %> <i>(leave blank if you don't want to change it)</i><br />
<%= f.password_field :password, autocomplete: "off" %>
</div>
<div class="field">
<%= f.label :password_confirmation %><br />
<%= f.password_field :password_confirmation, autocomplete: "off" %>
</div>
<div class="field">
<%= f.label :current_password %> <i>(we need your current password to confirm your changes)</i><br />
<%= f.password_field :current_password, autocomplete: "off" %>
</div>
<div class="actions">
<%= f.submit "Update" %>
</div>
<% end %>
<h3>Cancel my account</h3>
<p>Unhappy? <%= button_to "Cancel my account", registration_path(resource_name), data: { confirm: "Are you sure?" }, method: :delete %></p>
<%= link_to "Back", :back %>
[This is where error come][1]
[1]: http://i.stack.imgur.com/ulH9j.png when i try to call edit page.

Answer 1

Before avatar uploading there is no avatar assigned to user. First you must check is there any avatar. Your condition should look like this
current_user.avatar.presence? not current_user.avatar.url.presence?

Answer 2

I think it has to do with your avartar_uploader.rb file and how you are not including RMagick or MiniMagick support. Also, your storage direction won't work so I included the store_dir that works for me.
You need to add/fix the following code.
class AvatarUploader < CarrierWave::Uploader::Base
include CarriierWave:RMagick
storage :file
def store_dir
"uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
end
end
You can also use Cloudinary for file storage online. It works great with CarrierWave. Cloudinary is a cloud-based service that provides an end-to-end image management solution including uploads, storage, administration, image manipulation, and delivery.
Here is the documentation http://cloudinary.com/documentation/rails_carrierwave