ActionController::ParameterMissing (param is missing or the value is empty: item): - ruby-on-rails

Question

I have programmed an android app, which can take profile pictures from a user. Now I want to upload these profile picture to my Ruby on Rail server. However the upload doesn't work. I receive the Error message:
app/controllers/items_controller.rb:55:in `item_params'
app/controllers/items_controller.rb:21:in `create'
Started POST "/items" for 192.168.3.7 at 2016-09-11 01:12:21 +0900
Processing by ItemsController#create as HTML
Parameters: {"image"=>#<ActionDispatch::Http::UploadedFile:0x5737110 #tempfile=#<Tempfile:C:/Users/Clemens/AppData/Local/Temp/RackMultipart20160911-2
8624-1vjbftr.jpg>, #original_filename="IMG_20160911_010525.jpg", #content_type="application/octet-stream", #headers="Content-Disposition: form-data; na
me=\"image\"; filename=\"IMG_20160911_010525.jpg\"\r\nContent-Type: application/octet-stream\r\nContent-Transfer-Encoding: binary\r\n">}
Completed 400 Bad Request in 0ms (ActiveRecord: 0.0ms)
ActionController::ParameterMissing (param is missing or the value is empty: item):
app/controllers/items_controller.rb:55:in `item_params'
app/controllers/items_controller.rb:21:in `create'
Why does this not work? How should my item_params be defined? Here is my items_controller.rb
class ItemsController < ApplicationController
before_action :set_item, only: [:show, :edit, :update, :destroy]
# GET /items
# GET /items.json
def index
#items = Item.all
end
# GET /items/1
# GET /items/1.json
def show
send_data(item.file_contents,
type: #item.content_type,
filename: #item.filename)
end
# POST /items
# POST /items.json
def create
#item = Item.new(item_params)
if #item.save
render :show, status: :created, location: #item
else
render json: #item.errors, status: :unprocessable_entity
end
end
# PATCH/PUT /items/1
# PATCH/PUT /items/1.json
def update
if #item.update(item_params)
render :show, status: :ok, location: #item
else
render json: #item.errors, status: :unprocessable_entity
end
end
# DELETE /items/1
# DELETE /items/1.json
def destroy
#item.destroy
end
private
# Use callbacks to share common setup or constraints between actions.
def set_item
#item = Item.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def item_params
#######################params.require(:item).permit(:name, :description, :picture)
params.permit(:picture)
end
end
UPDATE: I renamed my image from android app and called it "item". Now the parameter error disappears. However a new error arises:
app/controllers/items_controller.rb:24:in `create'
Started POST "/items" for 192.168.3.7 at 2016-09-11 10:25:26 +0900
Processing by ItemsController#create as HTML
Parameters: {"item"=>#<ActionDispatch::Http::UploadedFile:0x53b1d30 #tempfile=#<Tempfile:C:/Users/Clemens/AppData/Local/Temp/RackMultipart20160911-3144-anlpp6.jpg>, #original_filename="IMG_20160911_100920.jpg", #co
ntent_type="application/octet-stream", #headers="Content-Disposition: form-data; name=\"item\"; filename=\"IMG_20160911_100920.jpg\"\r\nContent-Type: application/octet-stream\r\nContent-Transfer-Encoding: binary\r\n"
>}
Unpermitted parameter: item
(0.0ms) BEGIN
SQL (31.2ms) INSERT INTO `items` (`created_at`, `updated_at`) VALUES ('2016-09-11 01:25:26', '2016-09-11 01:25:26')
(0.0ms) COMMIT
Completed 500 Internal Server Error in 62ms (ActiveRecord: 31.2ms)
ActionView::MissingTemplate (Missing template items/show, application/show with {:locale=>[:en], :formats=>[:html], :variants=>[], :handlers=>[:raw, :erb, :html, :builder, :ruby, :jbuilder]}. Searched in:
* "C:/Benutzer/Clemens/RubymineProjects/rails-api-fileupload-tutorial-carrierwave-single/app/views"
):
app/controllers/items_controller.rb:24:in `create'
Any idea why I get this error? I put in views following line both in views\application\show.json.jbuilder and in views\items\show.json.jbuilder:
json.extract! #item, :locale=>[:en], :formats=>[:html], :variants=>[], :handlers=>[:raw, :erb, :html, :builder, :ruby, :jbuilder]
However I still get the same error.

Answer 1

What is happening is that this line:
params.require(:item).permit(:name, :description, :picture)
will raise an exception if you do not have an item in your params. When you are sending to your create action, apparently you do not have an item. I am also assuming that when you saw this error you didn't have that line commented.