My idiotic encounter with accepts_nested_attributes_for in Rails 3

I was using accepts_nested_attributes_for for the first times in Rails 3 to create forms that have fields from a parent model and its child model. I made a number of mistakes that make me feel like an idiot right now. Actually, the last one did but I saw it fit to blog about it in case anyone else finds themselves wasting an hour or more trying to get their forms to work.

N/B

• I was using Rails 3.0.5 and Ruby 1.8.7 (MRI)
• The Parent model had a has_one relationship to the child. (This shouldn’t matter though)

Mistake 1

In this case, my fields_for helper wasn’t evaluating to anything. The textfields and textareas were therefore not being created in the view. The issue was that in Rails 3, the helpers form_for and fields_for use <%= instead of <% !! I used the latter. (i)

Therefore, my form_for and fields_for helpers should have looked like this:

<%= form_for ......... %>
<%= fields_for ......... %>

This made the text fields visible but the values weren’t there.

Mistake 2

I didn’t make the attributes of the child model accessible to the parent model. This is done using attr_accessible and passing child_attributes.

e.g

def Dog < ActiveRecord::Base
has_one :puppy
accepts_nested_attributes_for :puppy
attr_accessible: puppy_attributes
end

Mistake 3 (Epic Fail)

Now this is the part that got me cursing all over the place. My form was being created using the variable from the controller rather than a symbol i.e

<%= form_for @dog do |f| %>

INSTEAD OF

<%= form_for :dog do |f| %>

The field_for was supposed to accept an object of the puppy model referenced from the @dog variable passed to the form. Problem is I was so frustrated by the fact that my text fields were empty that I started binging on Google search results and ended up with a fields_for that accepted the object of the puppy model as a symbol hahaha! yeah stupid.. i know. This is how it looked:

<%= fields_for :puppy do |puppy_fields| %>
<%= puppy_fields.text_field :breed %>
<% end %>

It obviously should have been like this:

<%= fields_for @dog.puppy do |puppy_fields| %>
<%= puppy_fields.text_field :breed %>
<% end %>

I’m going to cringe away in a dark corner now… Cheers!!

 

FTP file upload with custom port number in Rails

Its quite weird that I’ve never come across a scenario task that needed the involvement of FTP, at least as far as Rails is concerned. In this case, it involved a FTP PUSH whereby the application was to upload a file to a remote FTP Server. Its pretty simple:

ftp=Net::FTP.new
 ftp.passive = true
 ftp.connect("URL","PORT")
 ftp.login("USERNAME", "PASSWORD")
 ftp.putbinaryfile("/PATH/TO/FILE")
 ftp.close

In most cases, the port number defaults to 21 and hence you can use the open method instead of connect:

Net::FTP.open('URL') do |ftp|
 ftp.passive = true
 ftp.login('USERNAME', 'PASSWORD')
 ftp.putbinaryfile("/PATH/TO/FILE")

end

But in my case, the FTP server had a different command port hence had to use the connect method.  The other thing that’s worth mentioning is the passive flag. Rails sends files via FTP in active mode by default. In active mode, the server initiates a connection from its command port to the client through a random port (in the client). This method has issues because firewalls block the TCP connection from the server to the client.

In passive mode however, the client initiates both connections to the server, solving the problem of firewalls filtering the incoming data port connection to the client from the server.

Cheers!