how to use an array in form_for?

Question

I've got a user model which contains a field called, lets say, text1. In the users/new form I want to have 4 individual text boxes for this text1. In my model I will take values from these boxes and concatenate them together as comma separated values and store them in the DB. To give you an understanding, this is what I want.

<input type="text" name="user[text1][]" />
<input type="text" name="user[text1][]" />
<input type="text" name="user[text1][]" />
<input type="text" name="user[text1][]" />

How do I get this using form_for helper method? For now please don't worry yourself about the accessor method in the model, that is all taken care of. Thanks a ton.

Answer 1

Add few virtual attributes to your User model

class User < ActiveRecord::Base
  attr_accessor :text1_part1  
  attr_accessor :text1_part2  
  attr_accessor :text1_part3  
  attr_accessor :text1_part4

  def before_validation
      self.text1 = "#{self.text1_part1}#{self.text1_part2}#{self.text1_part3}#{self.text1_part4}"
  end
  # make sure you fill the correct values for
  # the text parts for an existing record.
  # This can be done by implementing `after_find` or overriding
  # `text1=`.
end  

In your view code use the new attributes instead of text1

<% form_for(:user) do |f| %>
   #some code
   <%= f.text_field :text1_part1>
   <%= f.text_field :text1_part2>
   <%= f.text_field :text1_part3>
   <%= f.text_field :text1_part4>
   #some code
   <%= f.submit "Save">
<% end %>

Answer 2

The previous answer gives a solution, so I am just providing some background as to why what you are asking for does not work they way you might hope.

You can indeed create a form with multiple input fields of the same name, and that data will be posted. However, when rails receives the post it automatically parameterizes the post data and/or url parameters. It essentially splits on the & and assigns the key/value pairs to the params hash. The outcome of this is that params[:user][:text1] (from your example) will have the value of the last instance of the user[text1] it encountered, since it is simply a value assignment to an existing key. You might want to dig into ActiveRecord multiparameter assignments to get an idea of how datetime attributes work, since they are similar to your use-case.

Answer 3

I am working on something similar and it sounds like maybe serialization is what you are looking for. Unfortunately I don't have my issues solved yet, so I can't provide anything more concrete.