Rails 3.1+ Nested Forms Issue: Can't mass-assi

I have a basketball app, where a Roster has many Players, and a Player can be on multiple Rosters.(Reason for many-to-many is for a Player-Roster archive)

Roster.rb

class Roster < ActiveRecord::Base
      belongs_to :team
      has_many :rosterizes
      has_many :players, :through => :rosterizes
      accepts_nested_attributes_for :players
      attr_accessible :jersey_number, :team_id, :class_year, :players
    end

Rosterizes.rb(poorly named I know...)

class Rosterize < ActiveRecord::Base
  belongs_to :player
  belongs_to :roster
  attr_accessible :player_id, :roster_id
end

Player.rb

class Player < ActiveRecord::Base
  has_many :rosterizes
  has_many :rosters, :through => :rosterizes
  validates_presence_of :first_name, :last_name
  attr_accessible :first_name, :last_name, :active
end

The View

<div class="well">
    <h2>New Player</h2>
    <%= simple_form_for @roster, :url =>player_added_team_path, :html => { :class => 'form-horizontal' } do |f| %>
        <%= f.simple_fields_for @new_player 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>

The paramaters I am sending to the controller:

"roster"=>{"player"=>{"first_name"=>"first name", "last_name"=>"last name"}, "class_year"=>"freshman", "jersey_number"=>"23", "team_id"=>"1"}, "commit"=>"Add To Team", "id"=>"1"}

Controller that is handling the Saving:

def player_added
   @team = Team.find(params[:id])

   #where the issue is happening
   @roster = @team.rosters.build(params[:roster])
   @roster.save
   ...

end

I have a work around using using the parameters, BUT I would like to understand what I am doing wrong here for future/learning purposes and why it is giving me: Can't mass-assign protected attributes

My work around(kinda hacky):

def player_added

    @team = Team.find(params[:id])
    @roster = @team.rosters.build(:class_year => params[:roster][:class_year], :jersey_number => params[:roster][:jersey_number])
    @new_player = @roster.players.build(:first_name => params[:roster][:player][:first_name], :last_name => params[:roster][:player][:last_name])

    @roster.save
    @new_player.save

    ...

end

I am using Simple_Form 2.0...

I know this is a lot of information, but thanks you in advance!

SOLUTION

Just incase anyone else is having same the same/similar issue I am...

I installed this plug in => https://github.com/ryanb/nested_form

So this is the changes I made:

Roster.rb

class Roster < ActiveRecord::Base
  belongs_to :team
  has_many :rosterizes
  has_many :players, :through => :rosterizes
  accepts_nested_attributes_for :players
  attr_accessible :jersey_number, :class_year, :players, :player_attributes
end

I also made the change to the view to:

 <%= simple_nested_form_for @roster, :url =>player_added_team_path, :html => { :class => 'form-horizontal' } do |f| %>
      <%= f.simple_fields_for :players, @roster.players.build do |x| %>
           # nested form
           ...
      <%end%>
      # form
      ...
<%end%>

Controller to save def player_added

@team = Team.find(params[:id])
@roster = @team.rosters.build(params[:roster])
@roster.save

...

end

This was a pain in the butt for me to understand, Hopefully this will cut down the time for any of you looking for answers/learning nested_forms!

The problem is with the way you are naming your nested association attribute, and with the parameters you are sending:

The attribute for nested :players should be :players_attributes, and :team_id should not be listed (because that overrides the team association rails magic):

attr_accessible :jersey_number, :class_year, :players_attributes

And the parameters should have this format:

"roster"=>{"players_attributes"=>[{"first_name"=>"first name", "last_name"=>"last name"}], "class_year"=>"freshman", "jersey_number"=>"23"}, "commit"=>"Add To Team", "id"=>"1"}

To accomplish this, you should probably change simple_form_for @roster to simple_nested_form_for @roster

Note that you don't need to include the "team_id" attribute in the parameters for "roster" because that you are already loading and associating the roster to it.