[Rails] Re: Select List to change type of STI class

[Wilson Bilkovich]

On 3/31/06, jacob smails <jsmails at yahoo.com> wrote:
> Wilson Bilkovich wrote:
> > On 3/30/06, jacob smails <jsmails at yahoo.com> wrote:
> >> But I get this error:
> >>
> >> wrong argument type String (expected Module)
> >>
> >
> > You can do something like this:
> > selected_type = params[:user][:type]
> > klass = selected_type.constantize
> > new_user = klass.new(params[:user])
>
> Actually, the part I was struggling with was how to create the drop-down
> list. I ended up just creating the list by hand (i.e. not using the form
> helper). Then, in the controller I reset the subclass and save like
> this:
>
> @user[:type] = params[:user][:type]
> if @user.save
>   etc...
>
> It seems to work fine, but I still don't understand the error I was
> getting using the "select" form helper. Any ideas?
>

Oh, I see. You could do it this way:
@available_user_types = %w(Administrator User SuperCoolHacker)
@type_options = @available_user_types.zip(@available_user_types)

..and then in your view, use the @type_options variable as the
parameter to the "select" helper.

Here's some code from the admin interface of an app I'm working on,
just in case it helps.
It needs to be simplified, but it might be a useful starting point. 
Can you tell I'm paranoid about form parameters?

  def new_item
    if params[:item]
      item_type = params[:item][:item_type]
      item_type = 'Item' if item_type.blank?
    else
      item_type = 'Item'
    end
    @item = item_type.constantize.new(params[:item])
    @item.community = @community

    if request.post? and @item.save
      flash[:notice] = "#{@item.item_type.titleize} was successfully created."
      redirect_to :action => 'show_item', :id => @item
    end
  end

..and in the rhtml template, this:
<%= select 'item', 'item_type', Item::ITEM_OPTIONS,
  {:prompt => "Select one:"}, :onchange => 'item_type_select();' %>

ITEM_OPTIONS is a constant in the superclass containing a
select-helper-compatible list of subclasses that users can choose
from.