如何在Rails应用程序中将file_field连接到上载操作

Question

I'm trying to add to a very simple data entry form, a button that allows the user to upload a file to the servers file system so that the url to that file can be placed in a field of the database.

So far, I've worked out that in the _form...erb file, I can add the file_field helper:

<%= form_for(@business) do |f| %>
<% if @business.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(@business.errors.count, "error") %> prohibited this business from being saved:</h2>

<ul>
<% @business.errors.full_messages.each do |msg| %>
<li><%= msg %></li>
<% end %>
</ul>
</div>
<% end %>

<div class="field">
<%= f.label :deletedFlag %><br />
<%= f.check_box :deletedFlag %>
</div>
<div class="field">
<%= f.label :name %><br />
<%= f.text_field :name %>
</div>

...

<div class="field">
<%= f.label :logoURL %><br />
<%= f.text_field :logoURL %>

    <%= f.file_field :imagefile %>
</div>

<div class="field">
<%= f.label :streetAddress %><br />
<%= f.text_area :streetAddress %>
</div>
<div class="actions">
<%= f.submit %>
</div>
<% end %>

This gives me a form with a "Choose file" button. Clicking on that allows the selection of the file. Great.

Now, from the ruby guide at: http://guides.rubyonrails.org/form_helpers.html#uploading-files I'm told to add something like:

def upload
  uploaded_io = params[:business][:imagefile]
  File.open(Rails.root.join('public', 'uploads', uploaded_io.original_filename), 'w') do |file|
    file.write(uploaded_io.read)
  end
end

to my controller.

What I haven't worked out is how that file_field gets connected to that 'upload' action. I can see in the logs that the button press accepts the filename, etc, but there's no indication that the file upload is started or attempted.

I've read a number of references, and they all seem to say that you need these two things, but (for me) they don't connect the dots. Yes I'm very new to Ruby/Rails, so I'm obviously missing something fundamental.

Answer 1

You probably need to setup a route so that Rails can pass the request from your form into your controller, then setting up your form to use that route:

# config/routes.rb
post '/upload' => 'mycontroller#upload'

# app/views/some_model/new.html.erb
<%= form_for something, url: upload_path do |f| %>
...

This is probably the least recommended way of handling a file upload on Rails, especially for a new user, though. You would be much better off setting up Carrierwave , Paperclip , or Dragonfly instead.

Answer 2

Did you forget to specify multipart in your form_for like this?

<%= form_for(@uploadfile, :html => {:multipart =>true}) do |f| %>

Check the generated form html code, do you see this?

<form ... enctype="multipart/form-data" ...>