Nested attributes for has_many relationship

Question

My models are

class History < ActiveRecord::Base
  belongs_to :projects_lkp
  has_many :pictures
  accepts_nested_attributes_for :pictures
end

class Picture < ActiveRecord::Base
  belongs_to :history
  validates_presence_of :pics
end

history/new.html.erb

<%= form_for(:history, :url => {:action => 'create'}) do |d| %>
  <%= render(:partial =>"form",:locals => {:d => d}) %>
<% end %>

history/_form.html.erb

<%= d.fields_for :pictures do |dd| %>   
  <div class="row form-group"></div>
    <div><class='col-md-5 form-label'>Photo</div>
    <%= dd.file_field :pic, multiple: true, :class => 'col-md-15' %>
  </div>
<% end %>     

history_controller

def create
  @history = History.new(history_params)
  @history.projects_lkp_id = params[:projects_lkps_id]
  respond_to do |format|
    if @history.save
      format.html{ redirect_to histories_path(id: @history.id), notice:"History added" }
    else
      @history = History.where(item: @history.item).all
      format.html { render 'index' }
    end
  end
end

def history_params
  params.require(:history).permit(:history,:date,:pic)
end

But when I tried to submit form, it says that unpermitted parameter :pictures

Parameter passing is:

 Parameters: {"utf8"=>"✓", "authenticity_token"=>"xE8d/mD1pXh/2AIKrZlRoL552iEBVZ7jkzLJB1kNZyE=", "history"=>{"history"=>" jhafjkaalkds", "date"=>"20/10/2014", "pictures"=>{"pic"=>[#<ActionDispatch::Http::UploadedFile:0x0000000143d1f8 @tempfile=#<Tempfile:/tmp/RackMultipart20150910-2753-1ml2hmf>, @original_filename="Firefox_wallpaper.png", @content_type="image/png", @headers="Content-Disposition: form-data; name=\"history[pictures][pic][]\"; filename=\"Firefox_wallpaper.png\"\r\nContent-Type: image/png\r\n">]}}, "projects_lkps_id"=>"", "commit"=>"Submit"}

Unpermitted parameters: pictures

Here the :pic is the attachment field created by using paperclip gem

Answer 1

I have found the answer for that :)

history controller

 def new
    @histories = History.new
   @histories.pictures.build
 end  

history/new

      <%= form_for(@histories, :url => {:action => 'create'}, html: {multipart:true})  do |d| %>
      <%= render(:partial =>"form",:locals => {:d => d}) %>
      <% end %>

it works :)