Can't mass-assign protected attributes: _destroy - ruby-on-rails

Question

I'm getting this really weird error when I submit my nested form.
Can't mass-assign protected attributes: _destroy
Any idea why this may be? It's a bit of a concern as I'm having to remove the 'destroy' hidden_field with javascript temporarily until i figure out what it is, meaning i can't delete anything!
_form.html.erb
<%= nested_form_for(#post, :html=> {:multipart => true, :class=> "new_blog_post", :id=> "new_blog_post"}) do |f| %>
<%= field do %>
<%= f.text_field :title, placeholder: "Give your post a title", :class=>"span12" %>
<% end %>
<%= field do %>
<%= f.text_area :body, placeholder: "Write something here...", :id=>"blog-text", :class=>"span12" %>
<% end %>
<%= f.label :search_locations, "Add locations to your post" %>
<%= text_field_tag :name,"",:class=>"localename", :id=>"appendedInput", :placeholder=> "Name of the location", :autocomplete => "off" %>
<%= f.link_to_add "Add a location", :locations %>
<%= actions do %>
<%= f.submit "Submit", :class=>"btn", :disable_with => 'Uploading Image...' %>
<% end end%>
_posts_controller.rb_
class PostsController < ::Blogit::ApplicationController
...
def new
#post = current_blogger.blog_posts.new(params[:post])
#location = #post.locations.build
end
def edit
#post = Post.find(params[:id])
##post = current_blogger.blog_posts.find(params[:id]) removed so any use can edit any post
#location = #post.locations.build
end
def create
location_set = params[:post].delete(:locations_attributes) unless params[:post][:locations_attributes].blank?
#post = current_blogger.blog_posts.new(params[:post])
#post.locations = Location.find_or_initialize_location_set(location_set) unless location_set.nil?
if #post.save
redirect_to #post, notice: 'Blog post was successfully created.'
else
render action: "new"
end
end
def update
#post = current_blogger.blog_posts.find(params[:id])
if #post.update_attributes(params[:post])
redirect_to #post, notice: 'Blog post was successfully updated.'
else
render action: "edit"
end
end
def destroy
#post = current_blogger.blog_posts.find(params[:id])
#post.destroy
redirect_to posts_url, notice: "Blog post was successfully destroyed."
end
location.rb
class Location < ActiveRecord::Base
after_save { |location| location.destroy if location.name.blank? }
has_many :location_post
has_many :posts, :through => :location_post
has_many :assets
attr_accessible :latitude, :longitude, :name, :post_id, :notes, :asset, :assets_attributes
accepts_nested_attributes_for :assets, :allow_destroy => true
include Rails.application.routes.url_helpers
def self.find_or_initialize_location_set(location_set)
locations = []
locations = locations.delete_if { |elem| elem.flatten.empty? }
location_set.each do |key, location|
locations << find_or_initialize_by_name(location)
end
locations
end
end
EDIT:
Snippet of rendered form in new.html.erb
<div class="row span locsearch">
<div class="input-append span3">
<input autocomplete="off" class="localename" id="appendedInput" name="name" placeholder="Name of the location" type="text" value="">
<span class="add-on"><input id="post_locations_attributes_0__destroy" name="post[locations_attributes][0][_destroy]" type="hidden" value="false"><i class="icon-trash"></i></span> </div>
<div class="latlong offset3 span4"> <p class="help-block">Enter the name of the town or city visited in this blog entry.</p>
</div>
<input class="LegNm" id="post_locations_attributes_0_name" name="post[locations_attributes][0][name]" type="hidden" value="Dresden">
<input class="long" id="post_locations_attributes_0_longitude" name="post[locations_attributes][0][longitude]" type="hidden" value="13.7372621">
<input class="lat" id="post_locations_attributes_0_latitude" name="post[locations_attributes][0][latitude]" type="hidden" value="51.0504088">
</div>
</div>
EDIT2:
post.rb
class Post < ActiveRecord::Base
require "acts-as-taggable-on"
require "kaminari"
acts_as_taggable
self.table_name = "blog_posts"
self.paginates_per Blogit.configuration.posts_per_page
# ==============
# = Attributes =
# ==============
attr_accessible :title, :body, :tag_list, :blogger_id, :coverphoto, :locations_attributes
# ===============
# = Photo Model =
# ===============
has_attached_file :coverphoto,
:styles => {
:coverbar => "600x300>", :medium => "250x250^" , :thumb => "100x100^"},
#:source_file_options => {:all => '-rotate "-90>"'},
:storage => :s3,
:s3_credentials => "#{Rails.root}/config/s3.yml",
:bucket => "backpackbug",
:path => "/:style/:id/:filename"
# ===============
# = Validations =
# ===============
validates :title, presence: true, length: { minimum: 6, maximum: 66 }
validates :body, presence: true, length: { minimum: 10 }
validates :blogger_id, presence: true
# =================
# = Associations =
# =================
belongs_to :blogger, :polymorphic => true
has_many :location_post
has_many :locations, :through => :location_post
belongs_to :profile
accepts_nested_attributes_for :locations, :allow_destroy => true, :reject_if => proc { |attributes| attributes['name'].blank? }
end end

Answer 1

This was solved with a combination of this and another answer, found here:
How can I fix this create function?
A short term fix is to add attr_accessible :_destroy and attr_accessor :_destroy.
Thanks both!

Answer 2

Add :_destroy to your attr_accessible list
attr_accessible ...., :_destroy

Answer 3

you should write to post.rb,
attr_accessible: locations_atributes
and
accepts_nested_attributes_for :locations, :allow_destroy => true
as you are updating the location object via post object.

Answer 4

replace f.hidden_field it must stay thus(line 2)
module ApplicationHelper
def link_to_remove_fields(name, f)
text_field_tag(:_destroy) + link_to_function(name, "remove_fields(this)")
end