Rails undefined method `model_name' for nil:NilClass nested routes - ruby-on-rails

Question

I'm a newbie on rails. My rails version is 4.2.6, simple_form_for version is 3.2.1. I want to redirect to the new page after I validated the params is false. And I get the error message.
undefined method `model_name' for nil:NilClass <%= simple_form_for
[:account, #station] do |f| %>
...
let me show you. This is my routes.rb
namespace :account do
resources :stations, expect: [:index]
end
stations_controller.rb
def new
#lines = Line.where(line_status: 1)
#station = Station.new
end
def create
unless check_post_params post_params
flash[:notice] = "miss params"
render action: :new # not work
# render :new # not work
# render 'new' # not work
# it work for me, but can I use render?
#redirect_to '/account/stations/new'
else
#station = Station.new(post_params)
if #station.save
redirect_to '/account/lines'
else
flash[:notice] = 'failed'
redirect_to 'account/stations/new'
end
end
end
private
def post_params
params.require(:station).permit(...)
end
def check_post_params(post_params)
if ...
return false
else
return true
end
end
_form.html.erb
<%= simple_form_for [:account, #station] do |f| %>
<div class="form-group">
<%= f.label :line_id, t('line.line_name') %>
<%= f.input_field :line_id,
... %>
<% end %>
The original I open the URL is http://localhost:3000/acoount/stations/new. After I click the submit, and I want to render :new, it will redirect to original URL, but I found the URL become http://localhost:3000/account/stations. The URL's /new is disappear. I have guessed it's about my routes.rb config.
And I tried to use rake routes to check my routes.
$ rake routes
...
POST /account/stations(.:format) account/stations#create {:expect=>:index]}
new_account_station GET /account/stations/new(.:format) account/stations#new {:expect=>[:index]}
...
I tried to use render account_stations_new_path and render new_account_station_path, but still not work for me. Thanks your help.
Edit
I know how to modify my code. I should validate my params on my model. And then I should use redirect_to not use render. I will update my code later.
Edit 2
I modified my model.
class Station < ActiveRecord::Base
belongs_to :line
has_many :spot_stations
validates :name, presence: true, uniqueness: { case_sensitive: false }
validates :line_id, presence: true
validates ....
end
And I modified my controller.
def new
# Because this #lines did't exist when I render 'new' on the create method. So I deleted it. And I create a method on the helper.
# #lines = Line.where(line_status: 1)
#station = Station.new
end
def create
#station = Station.new(post_params)
if #station.save
redirect_to '/account/lines'
else
flash[:notice] = 'failed'
render 'new'
end
end
I add a method for getting lines data
module Account::StationsHelper
def get_lines
#lines = Line.where(line_status: 1)
end
end
I will use it on my _form.html.erb
<%= simple_form_for [:account, #station] do |f| %>
<div class="form-group">
<%= f.label :line_id, t('line.line_name') %>
<%= f.input_field :line_id,
collection: get_lines,
label_method: :line_name,
input_html: { class: 'form-control' },
value_method: :id,
prompt: t('common.please_select') %>
</div>
...
<% end %>
This work great for me. Thanks your help.

Answer 1

try this:
if #station.save
redirect_to account_stations
else
flash[:notice] = 'failed'
render 'new'
end
as argument for render method you must pass action name, not url.