Cant get validation erros to work in Rails - ruby-on-rails

Question

I cannot get validation errors to work. I have a create product page which has two form_for's One for products and one for photos. When a product doesnt upload you get sent to redirect_to new_product_path
product controller
def new
#product = Product.new
#photo = Photo.new
end
def create
check_for_image = Photo.where(:product_id => nil, :user_id => current_user)
if check_for_images == []
redirect_to products_new_path, :notice => "Add an image then press start before submit"
else
#product = current_user.products.create(params[:product])
if #product.save
Photo.where(:product_id => nil, :user_id => current_user).update_all(:product_id => #product.id)
render "show", notice: "Product created!"
else
redirect_to new_product_path #, :flash => { :error => "Test!" }
# render "new"
end
end
end
I tried to do render "new" instead of redirect_to but i get undefined method `model_name' for NilClass:Class with the error pointing to the photo form for
haml create product page
= form_for #photo, :html => { :multipart => true, :id => "fd" } do |f|
%span Add files...
= f.file_field :image
= form_for #product,:url => products_path, :html => { id: "fd", multipart: true } do |f|
- if #product.errors.any?
.error_messages
%h2 Form is invalid
%ul
- for message in #product.errors.full_messages
%li
= message
%p
= f.text_field :name, placeholder: "Name"
%p
= f.text_field :price, class: "auto", data: { a_sign: "$ " }, placeholder: "Price"
%p
= f.text_field :description, placeholder: "Description"
%p.button.start
= f.submit
product model
validates :user_id, presence: true
validates :name, presence: true, length: { minimum: 5 }
validates :price, presence: true, numericality: { greater_than_or_equal_to: 3.00 }

Answer 1

I think first you need to know difference between redirect_to & render
redirect_to :action => 'new' #It will call the method 'new' and then it will call
#respective file. In this case it is `new.haml`
render :action => 'new' #It will call `new.haml` directly without calling method 'new'
So when you used render :action => 'new' it will not get #photo and hence it is giving error undefined methodmodel_name' for NilClass:Classeither you have to handlenil` on view or
It will fixed when you
Change
redirect_to new_product_path
To
#photo = Photo.new
render :action => 'new'

Answer 2

render will render a particular view using the instance variables available in the action. For example if a render was used for the new action, when a user goes to /new, the new action in the controller is called, instance variables are created and then passed to the new view. Rails creates the html for that view and returns it back to the user’s browser. This is what you would consider a normal page load.
redirect_to will send a redirect to the user’s browser telling it to re-request a new URL. Then the browser will send a new request to that URL and it will go through the action for that URL, oblivious to the fact that it was redirected to. None of the variables created in the action that caused the redirect will be available to the redirected view. This is what happens when you click on ‘Create’ in a form and the object is created and you’re redirected to the edit view for that object.
so you had no validation errors because each time you did a redirect a new instance was created with no errors.
2 lines you have to change:
render "show", notice: "Product created!"
and
redirect_to new_product_path
not sure about this:
redirect_to products_new_path, :notice => "Add an image then press start before submit" it's not clear what it does and how your app should behave.
your controller:
def new
#product = Product.new
#photo = Photo.new
end
def create
check_for_image = Photo.where(:product_id => nil, :user_id => current_user)
if check_for_images == []
redirect_to products_new_path, :notice => "Add an image then press start before submit"
else
#product = current_user.products.create(params[:product])
if #product.save
Photo.where(:product_id => nil, :user_id => current_user).update_all(:product_id => #product.id)
redirect_to #product, notice: "Product created!"
else
render action: "new"
end
end
end
more:
Are redirect_to and render exchangeable?
http://blog.markusproject.org/?p=3313