When editing a record that has a previously successfully uploaded image, how do I not have to re-upload on edit?

I am using Carrierwave, Fog to store images upload to S3.

The issue is that when I go to edit a record, the "file" & "photo" field automatically goes blank. So if I want to preserve the image or file in the record I have to re-upload it.

Otherwise, what happens is that the uploaded file/image just disappears. I am not even sure if it gets deleted from S3, but the association with my record in the db disappears.

This is my SimpleForm _form.html.erb partial for my Post model:

<%= simple_form_for(@post, html: {class: 'form-horizontal' }) do |f| %> 
    <%= f.error_notification %>
    <%= f.input_field :title, placeholder: "Enter Title"  %>
    <%= f.input_field :body, id: "body-field", placeholder: "Provide all the facts." %>
    <%= f.input_field :photo %>
    <%= f.input_field :file %>
    <%= f.button :submit, class: "btn btn-primary pull-left" %>
<% end %>

Here is my PhotoUploader

class PhotoUploader < CarrierWave::Uploader::Base
  include CarrierWave::RMagick
  storage :fog

  include CarrierWave::MimeTypes
  process :set_content_type

  def store_dir
    "images/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
  end

    version :main_thumb_mobile do
      process :resize_to_fit => [52, 52]
    end

    version :main_thumb do
      process :resize_to_fit => [150, 150]
    end

    version :post_thumb do
      process :resize_to_fit => [200, 200]
    end

    version :large do
      process :resize_to_limit => [400, 400]
    end

  def extension_white_list
    %w(jpg jpeg gif png)
  end
end

This is my FileUploader

class FileUploader < CarrierWave::Uploader::Base
  storage :fog
  def store_dir
    "files/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
  end

  def extension_white_list
    %w(pdf doc docx xls xlsx ppt pptx txt mp4 m4v mov avi mkv mp3 wav)
  end    
end

This is the Schema for my Post:

# == Schema Information
# truncated for brevity
# Table name: posts
#
#  id                    :integer          not null, primary key
#  title                 :text
#  photo                 :string(255)
#  body                  :text
#  user_id               :integer
#  file                  :string(255)

Edit 1

This is my Post.rb:

# == Schema Information
#
# Table name: posts
#
#  id                    :integer          not null, primary key
#  title                 :text
#  photo                 :string(255)
#  body                  :text
#  created_at            :datetime
#  updated_at            :datetime
#  user_id               :integer
#  ancestry              :string(255)
#  file                  :string(255)
#  status                :integer          default(0)
#  slug                  :string(255)
#  publication_status    :integer          default(0)
#  has_eyewitness        :boolean          default(FALSE)
#  youtube_embed_code    :text
#  soundcloud_embed_code :text
#

class Post < ActiveRecord::Base
  has_ancestry
  belongs_to :user
  resourcify
  enum status: [ :unconfirmed, :corroborated, :confirmed ]
  enum publication_status: [ :unpublished, :published ]
  extend FriendlyId
  friendly_id :title, use: [:slugged, :history, :finders]

  attr_accessor :country

  mount_uploader :photo, PhotoUploader
  mount_uploader :file, FileUploader

  validates_presence_of :body
  validates_length_of :body, maximum: 150, too_long: 'The report must be less than 150 words.',
                        tokenizer: ->(str) { str.scan(/\w+/) }
  validates_length_of :title, maximum: 7, too_long: 'The title must be less than 7 words.',
                                              tokenizer: ->(str) { str.scan(/\w+/) }

  def publish
    published!
  end

  def unpublish
    unpublished!
  end

  def is_published?
    if self.published?
      "yes"
    else
      "no"
    end
  end      
end

Edit 2

I changed the f.input_field :photo in my form to f.file_field :photo per jaspreet's suggestion and it still doesn't work. This is my log from an update request:

Started PATCH "/posts/ognr-takes-over-amcham-6a6f01ba-a9f9-44d5-924a-72f666f20ca8" for 127.0.0.1 at 2014-12-28 13:51:38 -0500
Processing by PostsController#update as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"S7FOq956fox6XYpar7Yd6V7AL+bwypQQxZktjHW3PNc=", "post"=>{"parent_id"=>"", "status"=>"unconfirmed", "publication_status"=>"unpublished", "title"=>"OGNR takes over AMCHAM", "body"=>"OGNR storms the rerl.", "has_eyewitness"=>"1", "youtube_embed_code"=>"", "soundcloud_embed_code"=>""}, "commit"=>"Update Post", "id"=>"ognr-takes-over-amcham-6a6f01ba-a9f9-44d5-924a-72f666f20ca8"}
  User Load (1.7ms)  SELECT  "users".* FROM "users"  WHERE "users"."id" = 1  ORDER BY "users"."id" ASC LIMIT 1
   (1.2ms)  SELECT COUNT(*) FROM "roles" INNER JOIN "users_roles" ON "roles"."id" = "users_roles"."role_id" WHERE "users_roles"."user_id" = $1 AND (((roles.name = 'admin') AND (roles.resource_type IS NULL) AND (roles.resource_id IS NULL)))  [["user_id", 1]]
   (6.4ms)  SELECT COUNT(*) FROM "roles" INNER JOIN "users_roles" ON "roles"."id" = "users_roles"."role_id" WHERE "users_roles"."user_id" = $1 AND (((roles.name = 'editor') AND (roles.resource_type IS NULL) AND (roles.resource_id IS NULL)))  [["user_id", 1]]
   (0.2ms)  BEGIN
  Post Exists (1.0ms)  SELECT  1 AS one FROM "posts" INNER JOIN "friendly_id_slugs" ON "friendly_id_slugs"."sluggable_id" = "posts"."id" AND "friendly_id_slugs"."sluggable_type" = 'Post' WHERE ("posts"."id" IS NOT NULL) AND "posts"."slug" = 'ognr-takes-over-amcham' LIMIT 1
  SQL (0.6ms)  INSERT INTO "posts" ("body", "created_at", "has_eyewitness", "slug", "soundcloud_embed_code", "title", "updated_at", "youtube_embed_code") VALUES ($1, $2, $3, $4, $5, $6, $7, $8) RETURNING "id"  [["body", "OGNR storms the rerl."], ["created_at", "2014-12-28 18:51:39.183091"], ["has_eyewitness", "t"], ["slug", "ognr-takes-over-amcham-cd491a8e-9a4e-4d5e-b13a-898de4adf135"], ["soundcloud_embed_code", ""], ["title", "OGNR takes over AMCHAM"], ["updated_at", "2014-12-28 18:51:39.183091"], ["youtube_embed_code", ""]]
  FriendlyId::Slug Load (0.5ms)  SELECT  "friendly_id_slugs".* FROM "friendly_id_slugs"  WHERE "friendly_id_slugs"."sluggable_id" = $1 AND "friendly_id_slugs"."sluggable_type" = $2  ORDER BY "friendly_id_slugs".id DESC LIMIT 1  [["sluggable_id", 43], ["sluggable_type", "Post"]]
  SQL (0.4ms)  DELETE FROM "friendly_id_slugs" WHERE "friendly_id_slugs"."sluggable_id" = $1 AND "friendly_id_slugs"."sluggable_type" = $2 AND "friendly_id_slugs"."slug" = 'ognr-takes-over-amcham-cd491a8e-9a4e-4d5e-b13a-898de4adf135'  [["sluggable_id", 43], ["sluggable_type", "Post"]]
  SQL (0.4ms)  INSERT INTO "friendly_id_slugs" ("created_at", "slug", "sluggable_id", "sluggable_type") VALUES ($1, $2, $3, $4) RETURNING "id"  [["created_at", "2014-12-28 18:51:39.242475"], ["slug", "ognr-takes-over-amcham-cd491a8e-9a4e-4d5e-b13a-898de4adf135"], ["sluggable_id", 43], ["sluggable_type", "Post"]]
   (2.6ms)  COMMIT
Redirected to http://localhost:3000/posts/ognr-takes-over-amcham-cd491a8e-9a4e-4d5e-b13a-898de4adf135
Completed 302 Found in 372ms (ActiveRecord: 17.3ms)

Edit 3

The PostController#Update looks like this:

class PostsController < ApplicationController
  load_and_authorize_resource

  def update
    respond_to do |format|
      if @post.update(post_params)
        format.html { redirect_to @post, notice: 'Report was successfully updated.' }
        format.json { render :show, status: :ok, location: @post }
      else
        format.html { render :edit }
        format.json { render json: @post.errors, status: :unprocessable_entity }
      end
    end
  end

Edit 4

The simplest solution I found is to simply add a check to see if there is a photo attached, like if @post.photo? and then just display a label if that is the case.

This, ofcourse assumes that I don't want to change the image.

<% if @post.photo? %>
    <label><%= @post.photo.file.filename %></label>
<% else %>
    <label for="photoFileUpload">Upload Images:</label>
    <%= f.input_field :photo %>
    <p class="help-block">Allowed: png, gif, jpg/jpeg</p>
<% end %>