Newbie question: getting scaffolding to handle belongs_to re

Rails
1

Sorry in advance if this question is very simple. I was looking for
advice or a link to help with the following issue.

Let’s say I have an app where I have categories of food like
‘Meat’,‘Dairy’,‘Fruit’ and the MVC functionality of this works well
already.

Now I create another sub-application where I add certain items of food
like ‘Orange’,‘Chicken’,‘Milk’, but I want to allow a user to pick
which category a particular item belongs to. Is there an automated way
of getting such an html select box with categories displayed?

BTW, I have successfully done this already, but I am afraid that I am
not harnessing the potential of RoR entirely here.

THANKS IN ADVANCE,
David

My sequence:

  1. create tables
  2. create models
  3. create scaffolding
  4. modify items_controller
  5. modify _form.html for items to allow for an html select to be
    created

Please offer any alternatives to what I have already done below:

tables= categories, items
–each have their own id
–items also has category_id

class Item < ActiveRecord::Base
belongs_to :category
validates_associated :category
end

class ItemsController < ApplicationController
def index
list
render :action => ‘list’
end

def list
@Item_pages, @Items = paginate :Item, :per_page => 10
end

def show
@Item = Item.find(params[:id])
end

def new
@categories=Category.find_all
@Item = Item.new
end

def create
@Item = Item.new(params[:Item])
if @Item.save
flash[:notice] = ‘Item was successfully created.’
redirect_to :action => ‘list’
else
@categories=Category.find_all
render :action => ‘new’
end
end

def edit
@categories=Category.find_all
@Item = Item.find(params[:id])
end

def update
@Item = Item.find(params[:id])
if @Item.update_attributes(params[:Item])
flash[:notice] = ‘Item was successfully updated.’
redirect_to :action => ‘show’, :id => @Item
else
render :action => ‘edit’
end
end

def destroy
Item.find(params[:id]).destroy
redirect_to :action => ‘list’
end
end

_form.rhtml
<%= error_messages_for ‘item’ %>

Item
<%= text_field 'item', 'item' %>

Description
<%= text_field 'item', 'description' %>

<%=options_from_collection_for_select @categories, "id", "category",@item.category_id%>

Created on
<%= datetime_select 'item', 'created_on' %>

Updated on
<%= datetime_select 'item', 'updated_on' %>

2

On 11/5/06, DavidB [email protected] wrote:

which category a particular item belongs to. Is there an automated way
of getting such an html select box with categories displayed?

Check out the Scaffolding Extensions plugin:
http://wiki.rubyonrails.com/rails/pages/Scaffolding+Extensions+Plugin

Jeremy

3

This question comes up a lot. The correct answer is that scaffolding is
not
meant to do that… it’s to get you started, not to build your app for
you.

http://blog.nicksieger.com/articles/2006/06/23/railsconf-amy-hoy-scaffolding

4

On 11/20/06, Brian H. [email protected] wrote:

This question comes up a lot. The correct answer is that scaffolding is not
meant to do that… it’s to get you started, not to build your app for you.

I wouldn’t say that’s the “correct answer.” It is the answer given by
Rails core members and certainly one of Rails opinions (this is the
reason it is called “scaffolding” in Rails). This “answer” is not
necessarily shared by others outside of the Rails community. For
example, in Django, usable production “scaffolding” is one of the main
features (it’s called the “Automatic admin interface”).

In my opinion, the main reason that the Rails community generally
frowns upon usable scaffolding is that Rails is primarily aimed at web
application production, whereas usable scaffolding mainly benefits
content site production (which is what Django is aimed at). As I
mainly administer content sites, usable production scaffolding saves
me a large amount of time. I use it on all of my sites, even ones
that are more application than content.

I do object to the idea that usable production scaffolding is
inherently bad. In fact, I can’t see any reason why you wouldn’t want
scaffolding to be as good as it can be, even if you then go on to
modify it.

For a lot of people, usable production scaffolding is a good thing.
That’s why there are a lot of plugins/generators devoted to it. I’m
not saying usable production scaffolding should be a core feature, as
it is in Django. However, I think that usable production scaffolding
doesn’t deserve the scorn that it often receives in the Rails
community.

Jeremy

5

@Jeremy:

Good points, all of them.

Scaffolding works for small sites. It works for the simple cases. When
you
start getting into situations where you have lots of relationships,
multiple
models per form, etc, it’s not going to cut it and you’re better off
just
writing it yourself because it’s not that hard.

THe main problem I have with scaffolding is that people see it and
expect to
be able to write big applications because it looks so easy. There are
tons
of things in the scaffolding that you just wouldn’t want in any
production
application, like the loops within loops, the lack of eager loading, and
the
pagination that really doesn’t work with large resultsets.

To me, scaffolding is something the newbies should use to see how things
work in Rails. I think it’s a neat excercise to see people writing
their
own scaffolding extensions, but I’ve seen time and time again that
generic
solutions just require too much work to modify to meet the current
situations. That’s why I like the fact that scaffolding in Rails does
very
little :slight_smile:

All good stuff though… thanks again for the thoughtful reply!

6

On 11/20/06, Brian H. [email protected] wrote:

Scaffolding works for small sites. It works for the simple cases. When you
start getting into situations where you have lots of relationships, multiple
models per form, etc, it’s not going to cut it and you’re better off just
writing it yourself because it’s not that hard.

Scaffolding works best for small sites, though it works fine for large
sites (using autocomplete for large tables). It’s true that it
doesn’t work with complex things like multiple models per form, but
lots of relationships isn’t a problem. Scaffolding is never going to
maximize the productivity when using a form, only when building it.
Scaffolding doesn’t solve hard problems, only tedious ones.

THe main problem I have with scaffolding is that people see it and expect to
be able to write big applications because it looks so easy. There are tons
of things in the scaffolding that you just wouldn’t want in any production
application, like the loops within loops, the lack of eager loading, and the
pagination that really doesn’t work with large resultsets.

True, scaffolding makes things look easy. That’s because using
scaffolding is easy, and if it solves your problems, there isn’t a
reason to do anything more difficult.

It’s also true that scaffolded code generally performs poorly.
However, it can handle eager loading, and performance of the
scaffolded forms themselves may not be an issue. It can be used as an
administrative front end to a high traffic site (particularly if
updates aren’t that frequent), though I would recommend custom coding
any forms that themselves get a lot of traffic.

To me, scaffolding is something the newbies should use to see how things
work in Rails. I think it’s a neat excercise to see people writing their
own scaffolding extensions, but I’ve seen time and time again that generic
solutions just require too much work to modify to meet the current
situations. That’s why I like the fact that scaffolding in Rails does very
little :slight_smile:

Generated scaffolding is useful as a teaching tool, but I find method
based scaffolding makes for easier maintenance. I find that if
scaffolding doesn’t meet your current needs, it’s better to extend
it’s capabilities than it does repeating yourself making small
modifications to a whole bunch of forms. In fact, I think the more
models you have, the more scaffolding is beneficial. Writing or
modifying CRUD forms for a 3 model site isn’t bad, but it’s pretty
mind numbing for an 100 model site.

Again, I think a lot of it depends on your needs. If you are writing
a complex web app with a lot of specialized forms, then it won’t help
much. If you are looking for an administrative front end to a content
site, it does the job quite well.

Jeremy

7

Thanks to all of you. As I look back at my question, I have already
learned how to do this and have learned what to expect from
scaffolding. Hopefully, other questions from me will challenge you
more, and hopefully I will soon contribute as well.

Thanks-David

8

Yes, my advice would be to just spend a little time using scaffolding to
orient yourself with some of the rails basics, then just move on. I
remember watching that blog on scaffolding screencast, and thinking it
looked so easy. But as soon as I started digging into the scaffold code
(without knowing much ruby or rails) I quickly got lost.

If you really need something quick and dirty, go with scaffolding. But
if you need anything beyond the default interface, or if you’re trying
to learn Rails, spend some time studying the scaffold code, then go
build your own. I don’t think the default code is worth modifying, and
you’ll be happier with (and prouder of) a custom solution.