Question

I need to create a form in my rails3 application that, when saved, will validate the fields and then submit them. I need a row for each field essentially.

The reason for this is that each ‘user’ has multiple attributes. For example:

• User-Password
• Expiration
• Access-Group

Have tried a nested form but that doesn’t really work for me.

In my console, this works pretty well for me:

user = Array.new
user << {:username => "jenny", :attribute_name => "User-Password", :value => "123"}
user << {:username => "jenny", :attribute_name => "Expiration", :value => "123"}
user << {:username => "jenny", :attribute_name => "Access-Group", :value => "123"}
User.create(user)

That inserts a number of rows, each with the same username but different attribute names and values. Perfect.

My problem is, how do I do this using a single form?? Initially I had a parent model and a nested form but I can’t figure it out.

Answer 1

This should actually be pretty straightforward nested form. Let us assume

class User
  has_many :attributes
  accepts_nested_attributes_for :attributes, :reject_if => :all_blank, :allow_destroy => true
end

class Attribute
  belongs_to :user
end

and an Attribute has an attribute_name, a value and a user_id.

Then your form, using haml, simple_form and cocoon would look like

= simple_form_for @user do
  = f.input :name
  #attributes
    = f.simple_fields_for :attributes do |attribute|
      = render 'attribute_fields', :f => attribute
    .links
      = link_to_add_association 'add new attribute', f, :attributes

and you add a partial called _attribute_fields.html.haml

.nested-fields
  = f.input :attribute_name
  = f.input :value
  = link_to_remove_association "remove attribute", f

If the attributes are fixed, you could easily change the input for attribute_name to

= f.input :attribute_name, :as => :select, :collection => {'User-Password', 'Expiration', 'Access-Group' }

If you want to read more about different types of nested forms, I have written a blogpost about it in greater detail.

[EDIT] Adding server-side validation to Attribute model:

Inside class Attribute you need to add:

validate :check_valid_values

def check_valid_values
  if attribute_name == 'Expiration'
    errors.add(:value, "Must be a valid date for Expiration") unless value.is_a_valid_date?
  end
end

Note that the method is_a_valid_date? does not exist, this is just to provide a small example. In this validation method you would then add all the possible attribute-value combinations with their validation.

Hope this helps.