ArgumentError for partial form, First argument in form cannot contain nil or be empty - forms

Question

My registration form was working just fine, but once I moved the registration from into a partial _signup.html.erb it has give me the error "First argument in form cannot contain nil or be empty"
I want to have the user registration from go through a modal from from the homepage instead of being redirected to new.html.erb.
static_pages/home.html.erb
<% else %>
<button type="button" class="btn btn-primary btn-lg" data-toggle="modal" data-target="#myModal">
Sign up with email
</button>
<div class="modal fade">
<div class="modal-dialog">
<div class="modal-content">
<div class="modal-header">
<button type="button" class="close" data-dismiss="modal" aria-label="Close"><span aria-hidden="true">×</span></button>
<h4 class="modal-title">Sign up</h4>
</div>
<div class="modal-body">
<%= render partial: 'users/signup', locals: {user: #user} %>
</div>
</div>
</div>
</div>
<% end %>
and in the partial _signup.html.erb
<div class="row">
<div class="col-md-6 col-md-offset-3">
<%= form_for(#user) do |f| %>
<form id="SignupForm">
<%= render 'shared/error_messages' %>
<fieldset>
<legend>Fill in your info</legend>
<%= f.label :username %>
<%= f.text_field :username, class: 'form-control' %>
<%= f.label :name %>
<%= f.text_field :name, class: 'form-control' %>
<%= f.label :email %>
<%= f.email_field :email, class: 'form-control' %>
<%= f.label :password %>
<%= f.password_field :password, class: 'form-control' %>
<%= f.label :password_confirmation %>
<%= f.password_field :password_confirmation, class: 'form-control' %>
<fieldset>
</fieldset>
<legend>Languages</legend>
<label for="Gender">Select gender</label>
<%= f.select :sex, options_for_select([['Select Gender', ''],['Male','1'],['Female','2']], "#{#user.sex}") %>
<label for="Country">Fill in your location</label>
<%= f.country_select :country_code, { priority_countries: ["GB", "US"] }, class: 'required-field', required: true %>
<%= f.submit "Create my account", class: "btn btn-primary" %>
<% end %>
</fieldset>
</form>
</div>
</div>
part of the users_controller.rb
class UsersController < ApplicationController
respond_to :html, :js
before_action :logged_in_user, only: [:index, :show, :edit, :update, :destroy]
before_action :correct_user, only: [:edit, :update]
before_action :admin_user, only: :destroy
def index
#users = User.paginate(page: params[:page])
end
def show
#user = User.find(params[:id])
#page_name = "user_page"
end
def new
#user = User.new
end
def signup
#user = User.new
end
def create
#user = User.new(user_params)
if #user.save
#user.send_activation_email
flash[:info] = "Please check your email to activate your account."
redirect_to root_url
else
render 'new'
end
end
def edit
#user = User.find(params[:id])
end
routes.rb
Rails.application.routes.draw do
root to: 'static_pages#home'
get 'help' => 'static_pages#help'
get 'about' => 'static_pages#about'
get 'contact' => 'static_pages#contact'
get 'signup' => 'users#new'
get 'login' => 'sessions#new'
post 'login' => 'sessions#create'
delete 'logout' => 'sessions#destroy'
get "users/signup" => 'users#signup'
resources :account_activations, only: [:edit]
resources :password_resets, only: [:new, :create, :edit, :update]
end

Answer 1

You don't have access to the instance variable #user in a partial. You have to pass it as a local variable:
static_pages/home.html.erb
<div class="modal-body">
<%= render partial: 'users/signup', locals: {user: #user} %>
</div>
And in your form partial you have to use that user local variable:
_signup.html.erb
<div class="row">
<div class="col-md-6 col-md-offset-3">
<%= form_for(user) do |f| %>
<form id="SignupForm">
<%= render 'shared/error_messages' %>
<fieldset>
<legend>Fill in your info</legend>
<%= f.label :username %>
<%= f.text_field :username, class: 'form-control' %>
<%= f.label :name %>
<%= f.text_field :name, class: 'form-control' %>
<%= f.label :email %>
<%= f.email_field :email, class: 'form-control' %>
<%= f.label :password %>
<%= f.password_field :password, class: 'form-control' %>
<%= f.label :password_confirmation %>
<%= f.password_field :password_confirmation, class: 'form-control' %>
<fieldset>
</fieldset>
<legend>Languages</legend>
<label for="Gender">Select gender</label>
<%= f.select :sex, options_for_select([['Select Gender', ''],['Male','1'],['Female','2']], "#{user.sex}") %>
<label for="Country">Fill in your location</label>
<%= f.country_select :country_code, { priority_countries: ["GB", "US"] }, class: 'required-field', required: true %>
<%= f.submit "Create my account", class: "btn btn-primary" %>
<% end %>
</fieldset>
</form>
</div>
</div>