Rails - Mar 2006 - [NQ] How to set an initial FK for a new item of something?

Hi all,

running into a little problem here. I''ve a list of things
with a "New thing" link beneath it. When you click that link,
obviously, a new thing shall be created. Now, that works pretty
fine for things that don''t have foreign keys, but for things that
do it crashes, since there is not yet a thing.other_thing.name
available.

I suspect you can somewhere in app/models/thing.rb tell it to
always assign, say, the first other_thing to a new thing... ?

Grateful for any hints you might have!

Best regards,
Raphael

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

Am Mittwoch, den 15.03.2006, 11:44 +0100 schrieb Raphael
Schmid:
> Hi all,
> 
> running into a little problem here. I''ve a list of things
> with a "New thing" link beneath it. When you click that link,
> obviously, a new thing shall be created. Now, that works pretty
> fine for things that don''t have foreign keys, but for things that
> do it crashes, since there is not yet a thing.other_thing.name
> available.
> 
> I suspect you can somewhere in app/models/thing.rb tell it to
> always assign, say, the first other_thing to a new thing... ?
> 
> Grateful for any hints you might have!
My head is so full of things, that it might help if can provide a code
example. That would help a lot to answer your question.

-- 
Norman Timmler

http://blog.inlet-media.de

> My head is so full of things, that it might help if can provide a code
> example. That would help a lot to answer your question.
Sure :-)

The flow is as follows:

---<snip: views/application/list.mab>---
[...]
link_to_remote(
  "New #{@label}",
  :url => {
    :controller => ''application'',
    :action => ''show_item'',
    :id => ''new'',
    :class => @helpers.params[:controller]
  }
)
[...]
---<snap>---

---<snip: controllers/application.rb>---
[...]
  def show_item
    controller = params[:class]
    action = controller.singularize
    klass = action.capitalize

    if params[:id] == ''new''
      item = Object.const_get(klass).new
    else
      item = Object.const_get(klass).find params[:id]
    end

    render :update do |p|
      p.replace_html ''item'', render(
        :partial => ''application/item'',
        :object => item,
        :locals => {
          :tpl => "#{controller}/#{action}"
        }
      )
    end
  end
[...]
---<snap>---

---<snip: views/application/_item.mab>---
[...]
  render :partial => tpl, :object => item
[...]
---<snap>---

---<example snip: views/contacts/_contact.mab>---
[...]
  contact.address      # <-- This works...
[...]
  contact.account.name # <-- Here''s the problem!
[...]
---<snap>---

The model looks like this (Account, of course, has_one :contact):

---<example snip: models/contact.mab>---
class Contact < ActiveRecord::Base
  belongs_to :account
  validates_presence_of :first_name
  validates_presence_of :last_name
  validates_presence_of :account_id
end
---<snap>---

That''s quite a lot of code now, hopefully it''ll help to
explain the
problem...

- Raphael

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

Am Mittwoch, den 15.03.2006, 15:02 +0100 schrieb Raphael
Schmid:
> > My head is so full of things, that it might help if can provide a code
> > example. That would help a lot to answer your question.
> 
> Sure :-)
> 
> The flow is as follows:
> 
> ---<snip: views/application/list.mab>---
> [...]
> link_to_remote(
>   "New #{@label}",
>   :url => {
>     :controller => ''application'',
>     :action => ''show_item'',
>     :id => ''new'',
>     :class => @helpers.params[:controller]
>   }
> )
> [...]
> ---<snap>---
> 
> ---<snip: controllers/application.rb>---
> [...]
>   def show_item
>     controller = params[:class]
>     action = controller.singularize
>     klass = action.capitalize
> 
>     if params[:id] == ''new''
>       item = Object.const_get(klass).new
>     else
>       item = Object.const_get(klass).find params[:id]
>     end
> 
>     render :update do |p|
>       p.replace_html ''item'', render(
>         :partial => ''application/item'',
>         :object => item,
>         :locals => {
>           :tpl => "#{controller}/#{action}"
>         }
>       )
>     end
>   end
> [...]
> ---<snap>---
> 
> ---<snip: views/application/_item.mab>---
> [...]
>   render :partial => tpl, :object => item
> [...]
> ---<snap>---
> 
> ---<example snip: views/contacts/_contact.mab>---
> [...]
>   contact.address      # <-- This works...
> [...]
>   contact.account.name # <-- Here''s the problem!
> [...]
> ---<snap>---
> 
> The model looks like this (Account, of course, has_one :contact):
> 
> ---<example snip: models/contact.mab>---
> class Contact < ActiveRecord::Base
>   belongs_to :account
>   validates_presence_of :first_name
>   validates_presence_of :last_name
>   validates_presence_of :account_id
> end
> ---<snap>---
> 
> That''s quite a lot of code now, hopefully it''ll help to
explain the
> problem...
Ok, i see. Your problem is simple to describe: You want to access 
attributes of an associated model, but you do not know, if an
association has already been set.

You have two options:

1. Associate an empty Account when Contact is created

# model !completely untested!
class Contact < ActiveRecord::Base
  after_create :create_account
end

2. Test if an model has been associated, before accessing its attributes

# view
<%= contact.account && contact.account.name %>

This will only call the name method, if contact.account is not nil.


Hope That helps.
-- 
Norman Timmler

http://blog.inlet-media.de

> 1. Associate an empty Account when Contact is created
> 
> # model !completely untested!
> class Contact < ActiveRecord::Base
>   after_create :create_account
> end
> 
> 2. Test if an model has been associated, before accessing its attributes
> 
> # view
> <%= contact.account && contact.account.name %>
> 
> This will only call the name method, if contact.account is not nil.
Okay.
That''ll help with making it not crash :-)

Thanks a million Norman!

-- Raphael

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