First argument in form cannot contain nil or be empty Hartl's Rails 4 Tutorial

Question

I\'m working through Michael Hartl\'s Rails tutorial, and I\'m running into an issue in section 7.3.3. I receive this error message:

ArgumentError in Users#         


        

Answer 1

In your new.html.erb you have specified form_for(@user) that means you need to have some value in instance variable @user before calling the new action.

You can do it in two ways :

one way is define an action new in your controller which would be called before rendering your new.html.erb layout. For eg:

def new
  @user = User.new
end

other way is that in your form itself you could specify something like

<%= form_for(User.new) do |f| %>

Defining it in your new action is more standard way of doing it.

Answer 2

I dont see a new action on you controller.

def new
  @user = User.new
end

I maybe made indirectly, but it couldn't hurt defining it yourself. From you title that may be why the @user variable is nil, it wasn't defined.

Answer 3

The order of actions in controller file matters. I had the same error until I figure out the problem on order of action methods. Example. Controller file

def edit
  @post = Post.find(params[:id])
end

def update

end

private
def post_params
    params.require(:post).permit(:title, :body)
end

I was working on edit action and was getting same error as you. The problem was I have written the edit action under private action. once I changed the order of this actions. It worked like a charm.

What I was trying to achieve ? I was trying to take the values of post instance variable and use it into html form.