Rails 3.1+ nested form model not rendering properly - ruby-on-rails

Question

I have a basketball app, where a Roster has many Players, and a Player belongs to a Roster.
Roster.rb
class Roster < ActiveRecord::Base
has_many :players
accepts_nested_attributes_for :players
attr_accessible :class_year, :jersey_number, :player_id, :team_id
end
Player.rb
class Player < ActiveRecord::Base
has_many :gamelogs
belongs_to :rosters
validates_presence_of :first_name, :last_name
attr_accessible :first_name, :last_name, :active
end
And my view that is only rendering first part of the form, but NOT the nested one
<div class="well">
<h2>New Player</h2>
<%= simple_form_for #new_player, :html => { :class => 'form-horizontal' } do |f| %>
<%=f.simple_fields_for :players do |x|%>
<%= x.input :first_name %>
<%= x.input :last_name %>
<%end%>
<%=f.input :class_year %>
<%=f.input :jersey_number %>
<%=f.input :team_id, :as => :hidden, :input_html => {:value => params[:id]}%>
<div class="well">
<%= f.button :submit, :class => 'btn-primary icon-plus-sign btn-success', :value => "Add To Team" %>
</div>
<%end%>
</div>
Image of it not working:
http://i.stack.imgur.com/Uoirp.png
I am using Simple_Form 2.0 and Twitter Boot Strap. Is there something I am not seeing? I feel like this should be simple, but I can't seem to figure out why it is not rendering. Thanks in advance.

Answer 1

You need an equal sign on your fields_for block:
<%= f.simple_fields_for :players do |x| %>
Edit:
All of this is assuming that #new_player == Roster.new
I had to do this with Formtastic, so it may be similar with Simple Form.
Looking at the source, it gives you an option to pass the nested object down to the nested form:
def simple_fields_for(record_name, record_object = nil, options = {}, &block)
So try doing something like this:
<%= f.simple_fields_for :players, #new_player.players.build do |x| %>