parsley/app/controllers/task_items_controller.rb

class TaskItemsController < ApplicationController

  before_action :ensure_valid_user
  before_action :set_task_list
  before_action :set_task_item, only: [:update, :destroy]

  def create
    @task_item = TaskItem.new(task_item_params)
    @task_item.task_list = @task_list

    if @task_item.save
      render :show, status: :created, location: [@task_list, @task_item]
    else
      render json: @task_item.errors, status: :unprocessable_entity
    end
  end

  def update
    if @task_item.update(task_item_params)
      render :show, status: :ok, location: [@task_list, @task_item]
    else
      render json: @task_item.errors, status: :unprocessable_entity
    end
  end

  def destroy
    @task_item.destroy
    head :no_content
  end

  private

  def task_item_params
    params.require(:task_item).permit(:name, :quantity, :completed)
  end

  def set_task_list
    @task_list = TaskList.find(params[:task_list_id])
    ensure_owner(@task_list)
  end

  def set_task_item
    @task_item = @task_list.task_items.find(params[:id])
  end

end