Rails - Jul 2008 - Another newbie - how to save related data?

Hello!  This has got to be one of those easy and obvious things, but
I''ve been beating my head against it for two days now, and
can''t figure
it out.

I''m following the tutorial at
http://www.tutorialspoint.com/ruby-on-rails-2.1/index.htm, which I have
found to be quite helpful.  However, I want to do things a little bit
differently, and can''t figure out how.  This tutorial sets up a
"Books"
table, with columns Title, Price, and Description.  There is another
table called "Subjects", with a column for Name.  The two tables have
a
one-to-many relationship, so the subject has many books.

The way the tutorial does it, you pre-populate the "Subjects" table
with
a list of subjects, and then when you create a form to enter new data,
you choose the subjects from a drop-down list.  I can get this to work
just fine, but I want to do something different: I don''t want the list
of subjects to be pre-determined, but I want to be able to enter them in
as I go.

How on earth do you do this?  I haven''t found a single tutorial that
explains how to enter data into a related table without using a
drop-down list of pre-entered data!

I can do it in the console:
>> s=Subject.new
=> #<Subject id: nil, name: nil, created_at: nil, updated_at:
nil>
>> s.name="Stuff"
=> "Stuff"
>> s.save
=> true
>> Subject.find(:all)
=> [#<Subject id: 1, name: "Stuff", created_at: "2008-07-31
20:35:58",
updated_at: "2008-07-31 20:35:58">]
>> Book.find(:all)
=> [#<Book id: 1, title: "Book", price: 5.0, subject_id: nil,
description: "Trying to figure this out.", created_at:
"2008-07-31
20:26:11", updated_at: "2008-07-31
20:26:11">]
>> b=Book.find(id="1")
=> #<Book id: 1, title: "Book", price: 5.0, subject_id: nil,
description: "Trying to figure this out.", created_at:
"2008-07-31
20:26:11", updated_at: "2008-07-31
20:26:11">
>> b.subject_id = "1"
=> "1"
>> b.save
=> true
>> Book.find(:all)
=> [#<Book id: 1, title: "Book", price: 5.0, subject_id: 1,
description:
"Trying to figure this out.", created_at: "2008-07-31
20:26:11",
updated_at: "2008-07-31 20:37:10">]

But for the life of me I can''t figure out how to do it using forms.

Any help is greatly appreciated!
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Hi Morgan,

Morgan Kay wrote:
> I want to do something different: I don''t want the list
> of subjects to be pre-determined, but I want to be able
> to enter them in as I go.
>
> How on earth do you do this?  I haven''t found a single
> tutorial that explains how to enter data into a related
> table without using a drop-down list of pre-entered
> data!
The key is in the documentation (api.rubyonrails.org) for "form_for"
where
it says " Also note that form_for doesn‘t create an exclusive scope. It‘s
still possible to use both the stand-alone FormHelper methods and methods
from FormTagHelper. "

The example that follows is not particulary helpful in your case since the
case all the items still address the same object.  That doesn''t need to
be
the case.  Everything in between the<% form for ...%> and <% end %>
is going
to show up in your params hash.  You''ll probably want to use a
text_field_tag for your subject entry field and then in your controller
method you''ll need to save that value to your Subjects table
separately.

HTH,
Bill


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Everything in between the<% form for ...%> and <% end %>
is
> going
> to show up in your params hash.  You''ll probably want to use a
> text_field_tag for your subject entry field and then in your controller
> method you''ll need to save that value to your Subjects table
separately.
> 
Bill, thank you so much for your reply!  I''m afraid I''m still
not quite
certain how to actually do this....  I have suspected in theory that I 
need to do what you describe, but I just don''t know what to actually 
do....

How do I save the value to the subjects table in the controller method? 
Do I define "create" in the subjects controller or the books
controller?
And what should the text_field_tag look like?

Sorry for the dumb questions, but I am totally new to this!  I''ve tried
reading the Ruby documentation, and most of the time it just doesn''t 
make much sense to me.  As you have no doubt heard other people 
complain, there are lots of tutorials/guides for people who know 
nothing, and lots of guides/documentation for experts, and really 
nothing in the middle, so once I''ve followed the instructions in the 
tutorials, launching out on my own is really tough!

Thanks for your help!
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Hi Morgan,
Morgan Kay wrote:
>
> How do I save the value to the subjects table in the controller method?
> Do I define "create" in the subjects controller or the books
controller?
> And what should the text_field_tag look like?
Starting from the last question and working up...

In your view, inside your <% form_for ... %> you''ll need

<%= text_field_tag ''subject'', "Enter book''s
subject:" %>

Technically you can create the new record in either controller because you
have access to all your models in each controller.  Since you''re
already in
your books controller, do it there.

Assuming you''re adding a new record, given the view above, after
you''ve
saved your book record, do something like ...

book_subject = Subject.new(params[:subject])
book_subject.save

HTH,
Bill


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Thanks again for your helpful and quick reply!

You seem to be using slightly different syntax than the tutorials I''ve 
been following, so I''m not quite sure if I''m following your
suggestion
correctly (this has been another major frustration in trying to learn 
this stuff - different tutorials use different syntax, so it''s really 
hard to apply what I learn in one tutorial to a different tutorial).

Here''s the relevant part of my books controller, more or less following
your suggestion (I tried it without the "@" as you suggested, and with
them as they appear below, and neither worked):

class BookController < ApplicationController
   ...
   def new
      @book = Book.new
   end
   def create
      @book = Book.new(params[:book])
      @book_subject = Subject.new(params[:subject])
      @book_subject.save
      if @book.save
            redirect_to :action => ''list''
      else
            render :action => ''new''
      end
   end
   ...
end


And here''s my new.html.erb:

<h1>Add new book</h1>
<% form_tag :action => ''create''  do %>
<p><label for="book_title">Title</label>:
<%= text_field ''book'', ''title''
%></p>
<p><label for="book_price">Price</label>:
<%= text_field ''book'', ''price''
%></p>
<p><label for="book_subject">Subject</label>:
<%= text_field ''subject'', ''name''
%></p>
<p><label
for="book_description">Description</label><br/>
<%= text_area ''book'', ''description''
%></p>
<%= submit_tag "Create" %>
<% end  %>
<%= link_to ''Back'', {:action =>
''list''} %>


Hitting the "Create" button works just fine, but no data is being
saved
to the Subject table.

Any idea what I need to do?

Thanks again!
Morgan
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Morgan Kay wrote:
> <%= text_field ''subject'', ''name''
%></p>
You need to use text_field_tag, not text_field, and you don''t need the
second param to text_field.  You''re still referencing it as a bound
parameter.  Doing it as I suggested moves the object outside the object
scope of the form and makes it available as a standalone param which is how
you''re referencing it in the controller.

HTH,
Bill


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> You need to use text_field_tag, not text_field, and you don''t need
the
> second param to text_field.  You''re still referencing it as a
bound
> parameter.  Doing it as I suggested moves the object outside the object
> scope of the form and makes it available as a standalone param which is 
> how
> you''re referencing it in the controller.
Oops, should have told you in the last post what happens when I do 
that...

When app/views/book/new.html.erb looks like this:

<h1>Add new book</h1>
<% form_tag :action => ''create''  do %>
<p><label for="book_title">Title</label>:
<%= text_field ''book'', ''title''
%></p>
<p><label for="book_price">Price</label>:
<%= text_field ''book'', ''price''
%></p>
<p><label for="book_subject">Subject</label>:
<%= text_field_tag ''subject'' %></p>
<p><label
for="book_description">Description</label><br/>
<%= text_area ''book'', ''description''
%></p>
<%= submit_tag "Create" %>
<% end  %>
<%= link_to ''Back'', {:action =>
''list''} %>

and I use the form to create a new entry with a subject, I get this 
error:

NoMethodError in BookController#create
undefined method `stringify_keys!'' for "stuff":String

I am really grateful for all your help, and sorry if I''m being dense!

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Morgan Kay wrote:

a) You didn''t let me know you''re using form_tag rather than
form_for as I
assumed repeatedly, explicitly, you were doing.

b)
> <%= text_field_tag ''subject'' %></p>
>
> and I use the form to create a new entry with a subject, I get this
> error:
>
> NoMethodError in BookController#create
> undefined method `stringify_keys!'' for "stuff":String
stuff?  Your console example used this for a value.  The error message above
says you''re now using it for a key.


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I can tell I have frustrated you... I''m doing my best, and I really 
appreciate everything you''re doing to help....
> a) You didn''t let me know you''re using form_tag rather
than form_for as
> I
> assumed repeatedly, explicitly, you were doing.
I am so incredibly lost.  Some tutorials have said to use "form_tag", 
some have said to use "form_for", and I don''t know the
difference.  I''m
sorry you made the wrong assumption, but I didn''t know enough to
correct
you.
> 
> b)
>> <%= text_field_tag ''subject'' %></p>
>>
>> and I use the form to create a new entry with a subject, I get this
>> error:
>>
>> NoMethodError in BookController#create
>> undefined method `stringify_keys!'' for
"stuff":String
> 
> stuff?  Your console example used this for a value.  The error message 
> above
> says you''re now using it for a key.
As I entered a sample entry, I used "stuff" as a sample subject.  It 
doesn''t matter what I put in the subject field - I get the same error 
message.

Obviously I''m being a total dunce here.  As I said in my first post, I 
have spent two days trying to figure this out, and I''m totally stymied.
I have read every book and tutorial and blog post I can find, and I just 
keep getting more and more confused.  Can you point me to a good place 
to learn about this?

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just curious..  morgan male or morgan female?

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I think I have faced this issue recently, and this worked for me.

Assumption:
I assumed that since it is belongs_to-has_many relationship, book
table would have a column "subject_id" mapped to subject table column
"id".

Changes:
I have changed couple of lines in your Controller code and changed the
view. It should work for you.

---------------Controller-----------:

def new
    @book = Book.new
end
def create
  @subject = (Subject.find_by_name(params[:subject][:name]) ||
Subject.create(params[:subject]))
  @book = Book.new(params[:book].merge(:subject_id => @subject.id))

  respond_to do |format|
   if @book.save
     redirect_to(:action => :list)
   else
     render :action => "new"
   end
  end
end

---------------View-------------
<% form_for(@book) do |f| %>

<p><label for="book_title">Title</label>:
<%= f.text_field ''title'' %></p>

<p><label for="book_price">Price</label>:
<%= f.text_field ''price'' %></p>

<p><label for="book_subject">Subject</label>:
<%= text_field(:subject, :name) %></p>

<p><label
for="book_description">Description</label><br/>
<%= f.text_area ''description'' %></p>

<p><%= f.submit "Create"%>
<%= link_to ''Back'', {:action =>
''list''} %></p>
<% end %>

On Jul 31, 10:30 pm, Morgan Kay
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> I can tell I have frustrated you... I''m doing my best, and I
really
> appreciate everything you''re doing to help....
>
> > a) You didn''t let me know you''re using form_tag
rather than form_for as
> > I
> > assumed repeatedly, explicitly, you were doing.
>
> I am so incredibly lost.  Some tutorials have said to use
"form_tag",
> some have said to use "form_for", and I don''t know the
difference.  I''m
> sorry you made the wrong assumption, but I didn''t know enough to
correct
> you.
>
>
>
> > b)
> >> <%= text_field_tag ''subject'' %></p>
>
> >> and I use the form to create a new entry with a subject, I get
this
> >> error:
>
> >> NoMethodError in BookController#create
> >> undefined method `stringify_keys!'' for
"stuff":String
>
> > stuff?  Your console example used this for a value.  The error message
> > above
> > says you''re now using it for a key.
>
> As I entered a sample entry, I used "stuff" as a sample subject. 
It
> doesn''t matter what I put in the subject field - I get the same
error
> message.
>
> Obviously I''m being a total dunce here.  As I said in my first
post, I
> have spent two days trying to figure this out, and I''m totally
stymied.
> I have read every book and tutorial and blog post I can find, and I just
> keep getting more and more confused.  Can you point me to a good place
> to learn about this?
>
> --
> Posted viahttp://www.ruby-forum.com/.
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Hi Morgan,

Morgan Kay wrote:
>
> I can tell I have frustrated you...
I apologize.  I should have exercised better judgement and waited until I
was in better humour to reply.  Not your fault at all.  Hope you''ll
forgive
me.
> I am so incredibly lost.  Some tutorials have said
> to use "form_tag",  some have said to use "form_for",
> and I don''t know the difference.
I''ve got a meeting this morning I''m still preparing for so
I''ll have to keep
this short for now.  I''ll check back after lunch.  The basic difference
between form_for and form_tag is that when you use the former you''re
telling
Rails, up front, which model the form will be referencing.  That impacts the
amount of ''magic'' Rails can do for you.  It seemed to me that
you were
expecting Rails to save the associated record (Subject) for you which is why
I assumed you were using form_for.  The reply from gouravtiwari21 uses
form_for and illustrates that ''magic''.  In thinking back on my
advice, I
don''t think the params assignment I suggested would have worked
correctly
for form_for anyway.  Probably should have worked for form_tag though.  But
I''ll have to get back to you later to go through that.
> Can you point me to a good place to learn about this?
If the tutorials aren''t helping, this is the right place ;-) 
I''ll check
back later.  Hang in there!

Best regards,
Bill


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gouravtiwari21 wrote:
> I think I have faced this issue recently, and this worked for me.
> 
> Assumption:
> I assumed that since it is belongs_to-has_many relationship, book
> table would have a column "subject_id" mapped to subject table
column
> "id".
> 
> Changes:
> I have changed couple of lines in your Controller code and changed the
> view. It should work for you.
> 
> ---------------Controller-----------:
> 
> def new
>     @book = Book.new
> end
> def create
>   @subject = (Subject.find_by_name(params[:subject][:name]) ||
> Subject.create(params[:subject]))
>   @book = Book.new(params[:book].merge(:subject_id => @subject.id))
> 
>   respond_to do |format|
>    if @book.save
>      redirect_to(:action => :list)
>    else
>      render :action => "new"
>    end
>   end
> end
> 
> ---------------View-------------
> <% form_for(@book) do |f| %>
> 
> <p><label for="book_title">Title</label>:
> <%= f.text_field ''title'' %></p>
> 
> <p><label for="book_price">Price</label>:
> <%= f.text_field ''price'' %></p>
> 
> <p><label for="book_subject">Subject</label>:
> <%= text_field(:subject, :name) %></p>
> 
> <p><label
for="book_description">Description</label><br/>
> <%= f.text_area ''description'' %></p>
> 
> <p><%= f.submit "Create"%>
> <%= link_to ''Back'', {:action =>
''list''} %></p>
> <% end %>
> 
> On Jul 31, 10:30 pm, Morgan Kay
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
This definitely looks closer to working than anything else I have tried! 
It makes so much sense to tell the controller what to do.  (Everything 
else I have read says "oh, just put has_may and belongs_to in the model 
and Rails will do everything for you!", and I have never quite believed 
that....)

I do have some questions, though.  First, just for clarification, in 
these lines:
>   @subject = (Subject.find_by_name(params[:subject][:name]) ||
> Subject.create(params[:subject]))
what are the "||" doing?  I don''t think I have seen that
before
anywhere....

Secondly, when I used this code, I went to ...books/new and got a No 
Method Error, so I had to add "map.resources :books" to 
config/routes.rb, and then it worked just fine.  Why does this happen? 
The tutorial that I have been following for this application never edits 
config/routes.rb, and the tutorial works just fine, but other tutorials 
I have followed don''t work without mapping resources.  I understand
what
adding "map.resources :books" does, I just don''t understand
why you
don''t have to do it for some applications, or which of your suggested 
changes made it necessary to do this.  (Does that question make sense? 
I can clarify if I need to....)

And finally, I can''t quite get this to work still.  When I hit the 
"Create" button, I get:
 NameError in BooksController#create
 uninitialized constant BooksController
I''ll keep chugging away trying to figure out why I''m getting
that error,
but if it''s something obvious, let me know.

Thanks so much for your help!
Morgan.
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Bill Walton wrote:
> I apologize.  I should have exercised better judgement and waited until 
> I
> was in better humour to reply.  Not your fault at all.  Hope
you''ll
> forgive
> me.
I certainly wasn''t in the most rational of moods myself - I was really 
really frustrated.  I''m feeling much more logical today.
> If the tutorials aren''t helping, this is the right place ;-) 
I''ll check
> back later.  Hang in there!
Thanks again for all your help and encouragement!
Morgan.
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I should say I haven''t explained it, was in hurry...but here is what I
meant:
> >  @subject = (Subject.find_by_name(params[:subject][:name]) ||
>> Subject.create(params[:subject]))
>what are the "||" doing?  I don''t think I have seen that
before
>anywhere....
Look closely at this line (  " || " is nothing but " or " ):
Subject.find_by_name(params[:subject][:name]) ||
Subject.create(params[:subject])

It reads:
'' find a Subject by subject name.
If do not find a subject then create the subject with object "
params[:subject] ". ''

Map Resources:
I think you have to add resources and good that you have added :)
>And finally, I can''t quite get this to work still.  When I hit the
>"Create" button, I get:
> NameError in BooksController#create
> uninitialized constant BooksController
It''s typo :)
I thought that your controller name is BooksController but it is
BookController

So you can do either of these:
1. Change your controller''s name from BookController to
BooksController (Looks appropriate to me)
or
2. If you do not change controller name then change your routes.rb :
map.resources :book

and restart server.

I think it should work.
Regards
gouravtiwari21
On Aug 1, 2:18 pm, Morgan Kay
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> gouravtiwari21 wrote:
> > I think I have faced this issue recently, and this worked for me.
>
> > Assumption:
> > I assumed that since it is belongs_to-has_many relationship, book
> > table would have a column "subject_id" mapped to subject
table column
> > "id".
>
> > Changes:
> > I have changed couple of lines in your Controller code and changed the
> > view. It should work for you.
>
> > ---------------Controller-----------:
>
> > def new
> >     @book = Book.new
> > end
> > def create
> >   @subject = (Subject.find_by_name(params[:subject][:name]) ||
> > Subject.create(params[:subject]))
> >   @book = Book.new(params[:book].merge(:subject_id => @subject.id))
>
> >   respond_to do |format|
> >    if @book.save
> >      redirect_to(:action => :list)
> >    else
> >      render :action => "new"
> >    end
> >   end
> > end
>
> > ---------------View-------------
> > <% form_for(@book) do |f| %>
>
> > <p><label for="book_title">Title</label>:
> > <%= f.text_field ''title'' %></p>
>
> > <p><label for="book_price">Price</label>:
> > <%= f.text_field ''price'' %></p>
>
> > <p><label
for="book_subject">Subject</label>:
> > <%= text_field(:subject, :name) %></p>
>
> > <p><label
for="book_description">Description</label><br/>
> > <%= f.text_area ''description'' %></p>
>
> > <p><%= f.submit "Create"%>
> > <%= link_to ''Back'', {:action =>
''list''} %></p>
> > <% end %>
>
> > On Jul 31, 10:30 pm, Morgan Kay
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
>
> This definitely looks closer to working than anything else I have tried!
> It makes so much sense to tell the controller what to do.  (Everything
> else I have read says "oh, just put has_may and belongs_to in the
model
> and Rails will do everything for you!", and I have never quite
believed
> that....)
>
> I do have some questions, though.  First, just for clarification, in
> these lines:>   @subject =
(Subject.find_by_name(params[:subject][:name]) ||
> > Subject.create(params[:subject]))
>
> what are the "||" doing?  I don''t think I have seen that
before
> anywhere....
>
> Secondly, when I used this code, I went to ...books/new and got a No
> Method Error, so I had to add "map.resources :books" to
> config/routes.rb, and then it worked just fine.  Why does this happen?
> The tutorial that I have been following for this application never edits
> config/routes.rb, and the tutorial works just fine, but other tutorials
> I have followed don''t work without mapping resources.  I
understand what
> adding "map.resources :books" does, I just don''t
understand why you
> don''t have to do it for some applications, or which of your
suggested
> changes made it necessary to do this.  (Does that question make sense?
> I can clarify if I need to....)
>
> And finally, I can''t quite get this to work still.  When I hit the
> "Create" button, I get:
>  NameError in BooksController#create
>  uninitialized constant BooksController
> I''ll keep chugging away trying to figure out why I''m
getting that error,
> but if it''s something obvious, let me know.
>
> Thanks so much for your help!
> Morgan.
> --
> Posted viahttp://www.ruby-forum.com/.
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Thank you for all of this information!  I''ve had a busy day, and
getting
ready to head out of town for the weekend, but I''ll come back to this
on
Monday.  Everything you have said makes a lot of sense.  Thanks!
Morgan.

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