Rails: Access params of a form with a nested model - ruby-on-rails

Question

I have the following models
class GymUser < ActiveRecord::Base
belongs_to :user
belongs_to :gym
end
class User < ActiveRecord::Base
has_many :gym_users
has_one :gym
attr_accessible :gym_users_attributes, :gym_users
accepts_nested_attributes_for :gym_users
end
I have a form for a new user, with a nested model gym_user. I want to make sure the user doesn't exist already. This is what I'm trying:
def create_member
#user = User.new(params[:user])
#user.generate_password
#dupe = User.find_all_by_email(#user.email)
if(#dupe)
#gym_user = GymUser.new(params[:user][:gym_users_attributes])
#gym_user.user_id = #dupe.id
elsif #user.save
#gym_user = #user.gym_users.order('created_at DESC').first
#gym = Gym.find(#gym_user.gym_id)
end
end
I know there's only one nested model here, but I can't figure out how to access those nested parameters.
Here's the form itself
<%= form_for #user, :as => :user, :remote => true, :url => { :controller => 'users', :action => 'create_member'} do |f| %>
<table border="0" cellpadding="10" cellspacing="0">
<tr>
<td colspan="2">
<%= f.label :name %><br />
<%= f.text_field :name %>
</td>
<td colspan="2">
<%= f.label :email %><br />
<%= f.text_field :email %>
</td>
</tr>
<% f.fields_for :gym_users do |builder| %>
<tr>
<td>
<%= builder.label :role_id, "Role" %><br />
<%= builder.collection_select(:role_id, #roles, :id, :name, {:include_blank => true}, {:onchange => "new_member_role_changed()"}) %>
<%= builder.hidden_field :gym_id, :value => #gym.id %>
</td>
<td>
<%= builder.label :item_id, "Membership Level" %><br />
<%= builder.collection_select(:item_id, #gym.membership_items, :id, :name, {:include_blank => true}) %>
</td>
<td>
<%= builder.label :has_monthly_billing, "Recurring Billing?" %><br />
<%= builder.radio_button :has_monthly_billing, "1" %>Yes
<%= builder.radio_button :has_monthly_billing, "0" %>No
</td>
<td>
<%= builder.label :billing_date %><br />
<%= builder.collection_select(:billing_date, (1..31).to_a, :to_s, :to_s, {:include_blank => true}) %>
</td>
</tr>
<tr>
<td colspan="4">
<%= f.submit %>
Cancel
</td>
</tr>
<% end %>
</table>
<% end %>

Answer 1

I found the answer. I'm not sure if this is the best way but it works
params[:user][:gym_users_attributes].values.first

Answer 2

Your association should be
has_one :gym, :through => gym_users
Also, can you post your form paramaters?

Answer 3

Your focus is on not allowing creation of duplicate users, and you are using email to verify this. You should rather use the helper
validates_uniqueness_of :email
in your User model. As you have a nested attribute, your object will be created only after Rails validates that a user with same email doesn't exist already.
I hope I understood your problem right.