When the form is submitted with an error, the rendered url changes in Rails 4

Question

I have created a user signup page. When the user submits the form incorrectly, when displaying a validation error, it does not render on the same URL.

The signup form is located at this url:

http://localhost:3000/signup

I have added the following routes for the signup page:

resources :users
match '/signup',  to: 'users#new', via: 'get'

When I submit the form, the model validation shows up but the url redirects to:

http://localhost:3000/users

I want the user to remain at the same url after submitting the form.

http://localhost:3000/signup

This is my controller code:

def new
    @user = User.new
  end

  def create

    @user = User.new(user_params) # Not the final implementation!

    if @user.save
      # Handle a successful save.
    else
        render 'new'
    end
  end

This is the beginning tag of my form:

<%= form_for @user, url: {action: "create"}  do |f| %>

Answer 1

I'm working with Rails 5, but I suspect it's not too different conceptually.

In routes.rb:

get 'signup', to: 'users#new'
post 'signup', to: 'users#create'
resources :users

and in your form helper:

<%= form_for @user, url: signup_path  do |f| %>

Essentially, the reason why it's not working as described in your original post is because when the form posts (rails 4.2 form helpers), it's tied to url: {action: "create"}, which by default, according to the routes automatically generated for resources :users, is post '/users', to: 'users#create (rails 4.2 routing guide). And by searching top down in routes.rb, it'll see this first and you end up with http://localhost:3000/users.

So, the changes I propose, should bind the form to post to the signup path instead which, in routes.rb, is seen as the second route entry.