Rails - Nov 2006 - Newbie question: getting scaffolding to handle belongs_to relationships

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'' %>

<!--[form:item]-->
<p><label for="item_item">Item</label><br/>
<%= text_field ''item'', ''item'' 
%></p>

<p><label
for="item_description">Description</label><br/>
<%= text_field ''item'', ''description'' 
%></p>

<p><select id="item_category_id"
name="item[category_id]">
<%=options_from_collection_for_select @categories, "id",
"category",@item.category_id%>
</select></p>

<p><label for="item_created_on">Created
on</label><br/>
<%= datetime_select ''item'', ''created_on'' 
%></p>

<p><label for="item_updated_on">Updated
on</label><br/>
<%= datetime_select ''item'', ''updated_on'' 
%></p>
<!--[eoform:item]-->


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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'' %>

<!--[form:item]-->
<p><label for="item_item">Item</label><br/>
<%= text_field ''item'', ''item'' 
%></p>

<p><label
for="item_description">Description</label><br/>
<%= text_field ''item'', ''description'' 
%></p>

<p><select id="item_category_id"
name="item[category_id]">
<%=options_from_collection_for_select @categories, "id",
"category",@item.category_id%>
</select></p>

<p><label for="item_created_on">Created
on</label><br/>
<%= datetime_select ''item'', ''created_on'' 
%></p>

<p><label for="item_updated_on">Updated
on</label><br/>
<%= datetime_select ''item'', ''updated_on'' 
%></p>
<!--[eoform:item]-->


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On 11/5/06, DavidB <davidbadawi-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
>
> 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?
Check out the Scaffolding Extensions plugin:
http://wiki.rubyonrails.com/rails/pages/Scaffolding+Extensions+Plugin

Jeremy

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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



On 11/20/06, Jeremy Evans
<jeremyevans0-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
>
>
> On 11/5/06, DavidB
<davidbadawi-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> >
> > 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?
>
> Check out the Scaffolding Extensions plugin:
> http://wiki.rubyonrails.com/rails/pages/Scaffolding+Extensions+Plugin
>
> Jeremy
>
> >
>

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On 11/20/06, Brian Hogan <bphogan-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
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

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@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 :)

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


On 11/20/06, Jeremy Evans
<jeremyevans0-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
>
>
> On 11/20/06, Brian Hogan
<bphogan-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 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
>
> >
>

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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.

-- 
Posted via http://www.ruby-forum.com/.

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On 11/20/06, Brian Hogan <bphogan-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
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 :)
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

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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


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