Cannot create new object in rails - ruby-on-rails

Question

I am trying to create a basic Item creation in rails but I am having trouble creating new item. I want to create item's name, say Wash the dishes. These are the codes that I have:
Routes:
resources :items
ItemsController:
class ItemsController < ApplicationController
...
def new
#item = Item.new
end
def create
#item = Item.new(item_params)
if #item.save
flash[:notice] = "Item was saved!"
redirect_to #item
else
flash.now[:alert] = "ERROR. ERROR."
render :new
end
end
...
private
def item_params
params.require(:item).permit(:name, :list_id)
end
end
items/new.html.erb
<%= form_for :item do |f| %>
<%= f.text_field :name %>
<%= f.submit %>
<% end %>
Lastly, schema:
create_table "items", force: :cascade do |t|
t.string "name"
t.integer "list_id"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
...
I got several different error codes, but this is the one I am currently stuck at (other times it showed different error code or it would simply prints out "ERROR. ERROR." (alert that I setup when save fails)
Routing Error
No route matches [POST] "/items/new"
When I go to rake routes:
POST /items(.:format) items#create
new_item GET /items/new(.:format) items#new
I followed suggestion from this SO post to check my routes and this is what I have:
2.2.2 :019 > r = Rails.application.routes
=> #<ActionDispatch::Routing::RouteSet:0x007fff323c3230>
2.2.2 :020 > r.recognize_path "/items/new"
=> {:controller=>"items", :action=>"new"}
I have also gone to rails c and I was able to create new item manually. (i = Item.new(name:"Test 123"); i.save)
What did I miss?

Answer 1

The problem is with your form. To understand what's wrong, do the following:
Start the rails server using rails s
Go to http://localhost:3000/items/new
Instead of filling in the form fields, view the source page
Check the form tag. Its submitting the form data to /items/new. ie.the action attribute is set to /items/new. Why is that?
From the documentation:
When the model is represented by a string or symbol, if the :url option is not specified, by default the form will be sent back to the current url (We will describe below an alternative resource-oriented usage of form_for in which the URL does not need to be specified explicitly).
<form action="/items/new" accept-charset="UTF-8" method="post">
In your routes.rb, there's no route matching POST /items/new
So, modify your form to
<%= form_for :item, url: items_path do |f| %>
<%= f.text_field :name %>
<%= f.submit %>
<% end %>
This generates a form tag which posts the data to /itemsrather than /items/new.
Or replace your form with
<%= form_for #item do |f| %>
<%= f.text_field :name %>
<%= f.submit %>
<% end %>
Now, the form will be submitted to /items. The advantage of using the second version is you can dry out your form for creating a new object and updating an existing object into a single view(partial).
For more, see http://guides.rubyonrails.org/form_helpers.html#binding-a-form-to-an-object

Answer 2

Try this in items/new.html.erb
<%= form_for #item do |f| %>
<%= f.text_field :name %>
<%= f.submit %>
<% end %>