Import CSV - No such file or directory - ruby-on-rails

Question

When I want to select a file via file_field, it gives me the error that my file is 'nil'. Here's the error: "No such file or directory - Book1.csv"
May I know why? Below are the codes:
controller
def import_csv
#list = List.find(params[:list_id])
#lists = List.all
respond_to do |format|
#csv_text = File.read(params[:list][:file])
#csv = CSV.parse(#csv_text, :headers => true)
#n=0
#csv.each do | row |
#user_new = User.new
#user_new.first_name = row[0]
#user_new.last_name = row[1]
#user_new.email = row[2]
#user_new.company = row[3]
#user_new.address = row[4]
#user_new.city = row[5]
#user_new.state = row[6]
#user_new.zipcode = row[7]
#user_new.country = row[8]
#user_new.notes = row[9]
#user_new.birthday = row[10]
#user_new.home_number = row[11]
#user_new.mobile_number = row[12]
#user_new.list_id = #list.id
#user_new.save
#list.subscribers += 1
#list.save
#n=#n+1
GC.start if #n%50==0
flash[:notice] = "CSV Imported Successfully, with #{#n} records"
end
format.html { redirect_to lists_url }
format.json { head :no_content }
end
end
view
<%= form_for(:list, :url => list_import_csv_path(#list), :method => :get, :html => {:multipart => true}) do |f| %>
<table>
<tr>
<td><label for="dump_file">Select a CSV File :</label></td>
<td><%= f.file_field :file %></td>
</tr>
<tr>
<td colspan='2'><%= submit_tag 'Import from CSV file' %></td>
</tr>
</table>
<% end %>

Answer 1

This is because you try to pass the ActionDispatch::Http::UploadedFile Object as a path instead of the real path. You do:
#csv_text = File.read(params[:list][:file])
you should do:
#csv_text = File.read(params[:list][:file].tempfile.to_path.to_s)
Also it might be a problem that you use :method => :get when you upload not so tiny files. Genereally GET and File Upload arent such a great combination.^^

Answer 2

6/27/2017 - Hopefully someone will benefit from this if they are in the same situation I was.
It turns out, whereas I had:
= form_tag action: :bulk_upload_submit, multipart: true do
...
= file_field_tag :file, accept: 'text/csv'
and it was sending the file params as:
"file"=>"subscribers.csv"
I needed to change the form_tag to use a path instead of an action:
= form_tag upload_subscribers_path, multipart: true do
which changed the params to:
"file"=>
#<ActionDispatch::Http::UploadedFile:0x007ffda857b5e0
#content_type="text/csv",
#headers="Content-Disposition: form-data; name=\"file\"; filename=\"subscribers.csv\"\r\nContent-Type: text/csv\r\n",
#original_filename="subscribers.csv",
#tempfile=#<File:/var/folders/_4/50fjk9z57x544klj30k0g1780000gn/T/RackMultipart20170627-33947-12xwfow.csv>>