rails 4 : use of form_for , no route, POST - ruby-on-rails

Question

started learning Ruby on Rails via Lynda - very excited and am trying my best to practice as much as possible. I am following the exercises but training is based on Rails 3 - through now some of the uses are not accepted.
Here is the situation:
I am reaching the create form at subjects/new
Filling out the form
get the following error in return
No route matches [POST] "/subjects/create"
Rails.root: /Users/alpozenalp/Sites/simple_cms
I spent the last 2 hours wandering around stackoverflow, rail guide and all other sources - tried many variations but can't get past this stage.
your help will be greatly appreciated.
routes.rb
SimpleCms::Application.routes.draw do
root :to => "demo#index"
get ':controller(/:action(/:id(.:format)))'
end
subjects_controller.rb
class SubjectsController < ApplicationController
def index
list
render('list')
end
def list
#subjects = Subject.order("subjects.position ASC")
end
def show
#subject = Subject.find(params[:id])
end
def new
#subject = Subject.new
end
def create
# Instantiate a new object using form parameters
#subject = Subject.new(params[:subject])
# Save the object
if #subject.save
# If save succeeds, redirect to the list action
redirect_to(:action => 'list')
else
# If save fails, redisplay the form so user can fix problems
render('new')
end
end
end
new.html.erb
<%= link_to("<< Back to List", {:action => 'list'}, :class => 'back-link') %>
<div class="subject new">
<h2>Create Subject</h2>
<%= form_for(:subject, :url => {:action => 'create'}, :method => :post) do |f| %>
<table summary="Subject form fields">
<tr>
<th>Name</th>
<td><%= f.text_field(:name) %></td>
</tr>
<tr>
<th>Position</th>
<td><%= f.text_field(:position) %></td>
</tr>
<tr>
<th>Visible</th>
<td><%= f.text_field(:visible) %></td>
</tr>
</table>
<div class="form-buttons">
<%= submit_tag("Create Subject") %>
</div>
<% end %>
</div>

Answer 1

naomik's answer will definitely help the form be cleaner, but it sounds like you just need to add a route for subjects in your config/routes.rb file:
SimpleCms::Application.routes.draw do
resources :subjects
root :to => "demo#index"
end
More info in the Rails routing guide.
Edit: Removed the default fallback route, per naomik's suggestion.

Answer 2

I have completed the course and my route.rb looks like below:
Cms2::Application.routes.draw do
root to: "public#index"
get 'admin', :to => 'access#menu'
get 'show/:id', :to => 'sections#show'
get ':controller(/:action(/:id(.:format)))'
post "admin_users/update"
post "subjects/update"
post "pages/update"
post "sections/update"
post "subjects/destroy"
post "subjects/create"
post "pages/destroy"
post "pages/create"
post "sections/destroy"
post "sections/create"
post "admin_users/destroy"
post "admin_users/create"
post "access/attempt_login"
get "access/logout"
end
My controller for def create is as follows:
def create
#new_position = params[:subject].delete(:position)
# Instantiate a new object using form parameters
#subject = Subject.new(params.require(:subject).permit(:name, :position, :visible, :created_at, :updated_at))
# Save the object
if #subject.save
##subject.move_to_position(new_position)
# If save succeeds, redirect to the list action
flash[:notice] = "Subject Created."
redirect_to(:action => 'list')
else
# If save fails, redisplay the form so user can fix problems
#subject_count = Subject.count +1
render('new')
end
end
Hope that helped!

Answer 3

You shouldn't have any problem if you just do
<%= form_for #subject do |f| %>
The form_for helper will automatically choose the correct (idiomatic) action and method based on the state of the model.
If #subject is a new record, you will get
<form action="/subjects" method="post">
...
If #subject is an existing record (with id: 1), you will get
<form action="/subjects/1" method="post">
<input type="hidden" name="_method" value="put">
...
Extra: Your list action seems completely pointless. Just use the index as intended.
Then this piece of code
<%= link_to("<< Back to List", {:action => 'list'}, :class => 'back-link') %>
Becomes this
<%= link_to '« Back to List'.html_safe, subjects_path, class: 'back-link' %>

Answer 4

I encountered the same problem at this point in the Lynda.com course. It was solved by adding resources :subjects above get ':controller(/:action(/:id(.:format)))', then changing the subjects_controller create action to
def create
#subject = Subject.new(params.require(:subject).permit(:name, :position, :visible))
if #subject.save
redirect_to(:action => 'list')
else
render('new')
end
end
This circumvented the Forbidden Attributes Error that occurred with the action as it was previously written.
Because I'd added resources :subjects, this then meant the redirect_to(:action => 'list') above would create an error along the lines of 'Couldn't find Subject with id=list'. To fix this, I added get 'subjects/list' => 'subjects#list' above the resources :subjects route (I've no idea if this was the 'right' thing to do, but it works for now).