Rails - Nested Form - ruby-on-rails

Question

I have Users who bet on matches. A single bet is called "Tipp" and the users predict the match score in "tipp.tipp1" and "tipp.tipp2"
I have problems with my form which is supposed to save "tipps" of users.
With the code below I get "Can't mass-assign protected attributes: tipp" although i have set "accepts_nested_attributes_for :tipps" and "attr_accessible :tipps_attributes".
I hope I have provided all the necessary code. Thanks in advance for your help!
Here is the parameters output:
Parameters:
{
"utf8"=>"✓",
"_method"=>"put",
"authenticity_token"=>"mPPpCHjA3f/M2l1Bd3ffO1QUr+kdETGkNE/0CNhbJXE=",
"user" =>{
"tipp"=>{
"6"=>{"tipp1"=>"4","tipp2"=>"6"},
"7"=>{"tipp1"=>"-1","tipp2"=>"-1"},
"8"=>{"tipp1"=>"-1","tipp2"=>"-1"}
}
},
"commit"=>"Update User",
"user_id"=>"1"
}
Shortened Code:
Controllers:
1) Users
class UsersController < ApplicationController
def edit_tipps
#user = current_user
end
def update_tipps
#user = current_user
if #user.update_attributes(params[:user])
flash[:notice] = "success (maybe)"
redirect_to user_edit_tipps_path(#user)
else
flash[:error] = "errors"
redirect_to user_edit_tipps_path(#user)
end
end
Models:
1) Users
class User < ActiveRecord::Base
attr_accessible :email, :password, :password_confirmation, :tipps_attributes
has_many :tipps
accepts_nested_attributes_for :tipps
end
2) Tipps
class Tipp < ActiveRecord::Base
attr_accessible :match_id, :points, :round_id, :tipp1, :tipp2, :user_id
belongs_to :user
end
My Form:
<%= form_for #user, :url => { :action => "update_tipps" } do |user_form| %>
<% #user.tipps.each do |tipp| %>
<%= user_form.fields_for tipp, :index => tipp.id do |tipp_form|%>
<%= tipp_form.text_field :tipp1 %><br/>
<%= tipp_form.text_field :tipp2 %><br/>
<% end %>
<% end %>
<%= submit_or_cancel(user_form) %>
<% end %>

Answer 1

Instead of doing what you did,
you could try either:
1.
Instead of:
<% #user.tipps.each do |tipp| %>
<%= user_form.fields_for tipp, :index => tipp.id do |tipp_form|%>
I would do this:
<%= user_form.fields_for :tipps do |tipp_form| %>
Or:
2.
class User < ActiveRecord::Base
attr_accessible :email, :password, :password_confirmation, :tipps_attributes, :tipps
Goodluck