undefined method 'class' after declare routes and relationships - ruby-on-rails

Question

i've been starting to learn rails and ruby. Im coding and app that one user has many buys and sell. I've been doing all the tutorials and looking for many answers here in SOF but without success so this is my issue:
NoMethodError in SellsController#create
undefined method `sell' for #
Where my user is "usuario" in spanish.
I know im missing something in somewhere because i already do this with the buys and works good. These are my files
Usuario.rb (Model)
class Usuario < ActiveRecord::Base
# Include default devise modules. Others available are:
# :confirmable, :lockable, :timeoutable and :omniauthable
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable
has_many :sells
has_many :buys
end
There is the "Has_many"
Sell.rb (Model)
class Sell < ActiveRecord::Base
belongs_to :usuario
after_create :set_estado
private
def set_estado
self.estado = true
end
end
That method is because Im trying to set the "estado" (Status) as true.
Sells Controller
class SellsController < ApplicationController
before_action :set_sell, only: [:show, :edit, :update, :destroy]
before_action :authenticate_usuario!
# GET /sells
# GET /sells.json
def index
#sells = Sell.all
end
# GET /sells/1
# GET /sells/1.json
def show
end
# GET /sells/new
def new
#sell = Sell.new
end
# GET /sells/1/edit
def edit
end
# POST /sells
# POST /sells.json
def create
#sell = current_usuario.sell.new(sell_params)
respond_to do |format|
if #sell.save
format.html { redirect_to #sell, notice: 'La venta ha sido creada con exito' }
format.json { render :show, status: :created, location: #sell }
else
format.html { render :new }
format.json { render json: #sell.errors, status: :unprocessable_entity }
end
end
end
# PATCH/PUT /sells/1
# PATCH/PUT /sells/1.json
def update
respond_to do |format|
if #sell.update(sell_params)
format.html { redirect_to #sell, notice: 'La venta ha sido modificada con exito.' }
format.json { render :show, status: :ok, location: #sell }
else
format.html { render :edit }
format.json { render json: #sell.errors, status: :unprocessable_entity }
end
end
end
# DELETE /sells/1
# DELETE /sells/1.json
def destroy
#sell.destroy
respond_to do |format|
format.html { redirect_to sells_url, notice: 'La venta ha sido eliminada con exito.' }
format.json { head :no_content }
end
end
private
# Use callbacks to share common setup or constraints between actions.
def set_sell
#sell = Sell.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def sell_params
params.require(:sell).permit(:usuario_id, :fecha_compra, :peso_final, :monto, :estado, :cantidad)
end
end
Im using scaffolds and the gem devise for authenticate.
I don't know what im missing because i have almost the same thing in buys and it's working but for sells doesnt work :(
My Routes.db
Rails.application.routes.draw do
devise_for :usuarios
devise_for :users
resources :usuarios do
resources :buys
resources :sells
end
get 'welcome/index'
post 'welcome/index'
post 'users/index'
resources :buys
resources :users
resources :sells
end
This is my first app on rails so i dont know what i missing now. Im using devise,Rails 4.2.1 and postgre as database

Answer 1

If your association is a has_many, Rails will use the plural form of the model as the association name. So instead of
current_usario.sell.new
try:
current_usario.sells.build
If you only expect one Sell per user, use a has_one association instead.
P.S. You might consider using "sales" instead of "sells", and "purchases" instead of "buys".