Forms for has_one but not always - ruby-on-rails

Question

I have two models: Personand User. A person can have a single user or no user at all, but every user have to be belong to a person.
I have set both models like so:
Person (has a has_user attribute):
has_one :user, dependent: :destroy
accepts_nested_attributes_for :user
User (has person_id attribute):
belongs_to :person
validates_presence_of :login, :password
validates_uniqueness_of :login
In the Person form I have a nested form_for that only shows up if I check a check box that also set the has_user attribute to true on the Person's form part.
My issue is that whenever I submit a person that has no user, it still tries to validate the user. How can I make it work?
UPDATE:
In my view:
<div class="form-group">
<%= person_form.label :has_user, :class => 'inline-checkbox' do %>
Possui usuário
<%= person_form.check_box :has_user, {id: "hasUser", checked: #person.has_user} %>
<% end %>
</div>
</div>
<div id="userPart" class="findMe"
<% if #person.user.id.blank? %> style="display:none;"
<% end %>>
<h2> User: </h2>
<div class="container">
<%= person_form.fields_for :user do |user_form| %>
<%= render partial: 'users/campos_user', locals: {form: user_form} %>
<% end %>
</div>
</div>
In my Person.js:
jQuery ->
$(document).ready ->
$(document).on 'turbolinks:load', #Added line
console.log("Turbolinks ready.")
$("#hasUser").change ->
$("#userPart").toggle();
return
return
return
return
In my Person Controller:
def new
#person= Contato.new
#person.ativo = true
#page_title = 'Novo person'
#person.build_user
end
def create
#person = Person.new(person_params)
respond_to do |format|
if #person.save
flash[:notice] = 'Contato foi criado com sucesso.'
if #person.has_user == true
format.html {redirect_to controller: :users, action: :new, person_id: #person.id}
else
format.html {redirect_to #person}
end
format.json {render :show, status: :created, location: #person}
else
flash[:warn] = "Erro ao criar contato."
format.html {render :new}
format.json {render json: #person.errors, status: :unprocessable_entity}
end
end
end
Person's params:
def person_params
params.require(:person).permit(:id, :company_id,
:active, :name,
:cargo, :celular,
:email, :nascimento,
:observacoes, :mensagem_instantanea,
:tipo_msg_inst, :possui_usuario,
user_attributes: [:login, :password, :permits, :id, :person_id, :_destroy])
end

Answer 1

You can reject submitting user attributes by using reject_if option
accepts_nested_attributes_for :user, :reject_if => :no_user_connected
def no_user_connected(attributes)
attributes[:user_attributes][:login].blank?
end
This should discard the user part of the form (all user attributes). Please note that I dunno how your form or controller looks like, so you might need to build the condition differently.
You can also make the validations on user conditional. But overall the best way to avoid convoluted validation problems is to use some kind of form objects where you encapsulate the validations process. https://thoughtbot.com/blog/activemodel-form-objects