Rails - Oct 2004 - Splitting an application into several objects with individual logic

Hello,

I am new to rails and got stuck when I wanted to develop some general 
purpose objects to be reused among several applications. These 
objects would then allow a programming style similar to GUI widget 
toolkits programming, by instantiating such a widget, set some of its 
attributes and then tell it to draw itself at the desired place.

I tried the following:

,--[controller/mywidget_controller]--
|require ''abstract_application''
|class MyWidgetController < AbstractApplicationController
|  def show
|    render "mywidget/show"
|  end
|end
''--

,-[controller/mainapp_controller]--
|require ''abstract_application''
|require ''mywidget_controller''
|class MainAppController < AbstractApplicationController
|  def index
|    show
|  end
|  def show
|    @widget=MyWidgetController.new()
|    render "mainapp/show"
|  end
|end
''--

,--[views/mainapp/show]--
|[html stuff]
|<%= @widget.show %>
|[more html stuff]
''--

...and expected views/mywidget/show to be rendered inside teh mainapp body.

But that was not the case, I got some errors, pasting the relevant part of the
backtrace:
Showing /home/show.rhtml where line #9 raised undefined method
`file_exists?'' for nil:NilClass
[offending line: 9: <%= @widget.show %>]

vendor/actionpack/lib/action_controller/base.rb:603:in
`template_exists?''
vendor/actionpack/lib/action_controller/base.rb:607:in
`assert_existance_of_template_file''
vendor/actionpack/lib/action_controller/base.rb:275:in `render_file''
vendor/actionpack/lib/action_controller/layout.rb:142:in `render''
/../app/controllers/mywidget_controller.rb:7:in `show''
(erb):9:in `render_template''
vendor/actionpack/lib/action_view/erb_template.rb:90:in
`render_template''
vendor/actionpack/lib/action_view/abstract_template.rb:34:in
`render_file''
vendor/actionpack/lib/action_controller/base.rb:279:in `render_file''
vendor/actionpack/lib/action_controller/layout.rb:142:in `render''
/../app/controllers/mainapp_controller.rb:13:in `show''
/../app/controllers/mainapp_controller.rb:9:in `index''

I suppose I tackled the problem entirely wrong, so can somebody help me
on how to achieve my initial goal?

Thanks in advance and regards,
Sebastian

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On Sun, 2004-10-31 at 19:17, Sebastian Ley wrote:
> Hello,
> 
> I am new to rails and got stuck when I wanted to develop some general 
> purpose objects to be reused among several applications. These 
> objects would then allow a programming style similar to GUI widget 
> toolkits programming, by instantiating such a widget, set some of its 
> attributes and then tell it to draw itself at the desired place.
Try this (untested):

1. Place widget.rhtml in app/views/shared/_widget.rhtml (template with
underscore is know as a partial). It should refer to widget variable for
any data that it needs.

2. Define widget class in lib/widget.rb (or even
app/controllers/widget.rb

3. Somewhere in the MyAppController#show, instantiate a Widget and
assign it to @widget.

4. In app/views/my_app/show.rhtml include <%= render_partial
''shared/widget.rhtml'', @widget.

You can also look at how NavBar and PostMenu are implemented in RForum -
these are exactly the kind of objects that you are asking about.

Alex

* Alexey Verkhovsky wrote:

[about partials]

Thanks, I believe that is what I was looking for ;-)
However:
> 4. In app/views/my_app/show.rhtml include <%= render_partial
> ''shared/widget.rhtml'', @widget.
...the lookup for shared partial templates seems to be broken:

<%= render_partial "listform/show", @personlist %>

results in:
Showing /home/show.rhtml where line #9 raised No such file or directory 
-
/var/www/rails/public/../config/environments/../../app/views//home/_listform/show.rhtml

-> Instead of searching in /views/listform/_show it searches 
for /view/$originaltemplate/listform/_show.

This neither according to API documetation nor to what I would expect. Suppose 
it is a bug?

Regards,
Sebastian

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You might need to have to update your rails, i believe this was fixed 


On Mon, 01 Nov 2004 00:36:52 +0100, Sebastian Ley
<sebastian.ley-uhhZ63b/5Phaq5fyzuukUWfrygkm6VTR@public.gmane.org>
wrote:
> * Alexey Verkhovsky wrote:
> 
> [about partials]
> 
> Thanks, I believe that is what I was looking for ;-)
> However:
> 
> > 4. In app/views/my_app/show.rhtml include <%= render_partial
> > ''shared/widget.rhtml'', @widget.
> 
> ...the lookup for shared partial templates seems to be broken:
> 
> <%= render_partial "listform/show", @personlist %>
> 
> results in:
> Showing /home/show.rhtml where line #9 raised No such file or directory
> -
/var/www/rails/public/../config/environments/../../app/views//home/_listform/show.rhtml
> 
> -> Instead of searching in /views/listform/_show it searches
> for /view/$originaltemplate/listform/_show.
> 
> This neither according to API documetation nor to what I would expect.
Suppose
> it is a bug?
> 
> 
> 
> Regards,
> Sebastian
> 
> --
> PGP-Key: http://www.mmweg.rwth-aachen.de/~sebastian.ley/public.key
> Fingerprint: A46A 753F AEDC 2C01 BE6E  F6DB 97E0 3309 9FD6 E3E6
> 
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
> 

-- 
Tobi

* Tobias Luetke wrote:
> You might need to have to update your rails, i believe this was fixed
Actually it was not even implemeted in the version I used before ;-) Thanks.

Okay, on my way to enlightenment I stumbled over the next problem:

With render_partial I can pass a local variable, which will in my case be the 
logic object I instantiated in the controller. E.g.

@widget=Widget.new()
[...]
<%= render_partial "widget/_showpartial" @widget %>

While this works fine now, there is still a problem: In
"widget/_showpartial"
I need to know the variable name I passed with render_partial, because I need 
to access it under that name. I can "work around" that by enforcing
that name
i.e. the render_partial function of that template needs always to be called 
with a variable named @widget.

However then I would not be able to use the same widget twice or more time in 
the same context, as all instances need to have the same name.

A solution would be that render_partial copied the variable in its argument to 
a common name for use in the template. Then, the templates could access the 
passed variable always under the same name.

Or am I missing the point...?

Regards,
Sebastian

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If you pass in a variable to render_partial you can access it under
the same name as the partial base filename. In your case probably
_showpartial ( i would suggest not using an underscore if you supply a
full path to the partial ).

The partials also share the entire instance variables ( e.g.
everything starting with @ ) with the main template.




On Mon, 01 Nov 2004 14:28:46 +0100, Sebastian Ley
<sebastian.ley-uhhZ63b/5Phaq5fyzuukUWfrygkm6VTR@public.gmane.org>
wrote:
> * Tobias Luetke wrote:
> > You might need to have to update your rails, i believe this was fixed
> 
> Actually it was not even implemeted in the version I used before ;-)
Thanks.
> 
> Okay, on my way to enlightenment I stumbled over the next problem:
> 
> With render_partial I can pass a local variable, which will in my case be
the
> logic object I instantiated in the controller. E.g.
> 
> @widget=Widget.new()
> [...]
> <%= render_partial "widget/_showpartial" @widget %>
> 
> While this works fine now, there is still a problem: In
"widget/_showpartial"
> I need to know the variable name I passed with render_partial, because I
need
> to access it under that name. I can "work around" that by
enforcing that name
> i.e. the render_partial function of that template needs always to be called
> with a variable named @widget.
> 
> However then I would not be able to use the same widget twice or more time
in
> the same context, as all instances need to have the same name.
> 
> A solution would be that render_partial copied the variable in its argument
to
> a common name for use in the template. Then, the templates could access the
> passed variable always under the same name.
> 
> Or am I missing the point...?
> 
> 
> 
> Regards,
> Sebastian
> 
> --
> PGP-Key: http://www.mmweg.rwth-aachen.de/~sebastian.ley/public.key
> Fingerprint: A46A 753F AEDC 2C01 BE6E  F6DB 97E0 3309 9FD6 E3E6
> 
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
> 

-- 
Tobi

* Tobias Luetke wrote:
> If you pass in a variable to render_partial you can access it under
> the same name as the partial base filename. In your case probably
> _showpartial
Hm, I suppose that would be what I am looking for, but it does not seem to 
work:

Showing /listform/_showpartial.rhtml where line #1 raised undefined local 
variable or method `_showpartial'' for
#<ActionView::Base:0x4067de84>
[...]
1: <a href="<%= _showpartial.origuri %>">Original
URI</a>

In the invoking template I passed a variable named @personlist whose class has 
a method name origuri and if I put the following in listform/_showpartial it 
does what is expected:
<a href="<%= @personlist.origuri %>">Original
URI</a>

But this is exactly what I want to avoid: In the shared partial I want to have 
no assumptions on the passed variable names...
> ( i would suggest not using an underscore if you supply a 
> full path to the partial ).
It is still needed, because it will substituted for the lookup:

where line #9 raised No rhtml or rxml template found for listform/_showpartial 
[...]
9: <%= render_partial "listform/showpartial", @personlist %>
> The partials also share the entire instance variables ( e.g.
> everything starting with @ ) with the main template.
Ok, but for my specific case I need to access the passed variables under a 
name independent from the name that was passed.

(Oh man, I barely understand it myself when I read all that, I hope you can 
make something out of it ;-) )

Regards,
Sebastian

-- 
PGP-Key: http://www.mmweg.rwth-aachen.de/~sebastian.ley/public.key
Fingerprint: A46A 753F AEDC 2C01 BE6E  F6DB 97E0 3309 9FD6 E3E6

I did a quick test:

file: app/view/test/_test.rhtml :
<%= test %>

random other view:
<%= render_partial ''test/test'', "hello world"
%>

printed : "hello world"

Hope this helps.
If you have any other problems you should come to IRC, I can help you
there directly ( in german, too )

On Mon, 01 Nov 2004 16:43:55 +0100, Sebastian Ley
<sebastian.ley-uhhZ63b/5Phaq5fyzuukUWfrygkm6VTR@public.gmane.org>
wrote:
> * Tobias Luetke wrote:
> > If you pass in a variable to render_partial you can access it under
> > the same name as the partial base filename. In your case probably
> > _showpartial
> 
> Hm, I suppose that would be what I am looking for, but it does not seem to
> work:
> 
> Showing /listform/_showpartial.rhtml where line #1 raised undefined local
> variable or method `_showpartial'' for
#<ActionView::Base:0x4067de84>
> [...]
> 1: <a href="<%= _showpartial.origuri %>">Original
URI</a>
> 
> In the invoking template I passed a variable named @personlist whose class
has
> a method name origuri and if I put the following in listform/_showpartial
it
> does what is expected:
> <a href="<%= @personlist.origuri %>">Original
URI</a>
> 
> But this is exactly what I want to avoid: In the shared partial I want to
have
> no assumptions on the passed variable names...
> 
> > ( i would suggest not using an underscore if you supply a
> > full path to the partial ).
> 
> It is still needed, because it will substituted for the lookup:
> 
> where line #9 raised No rhtml or rxml template found for
listform/_showpartial
> [...]
> 9: <%= render_partial "listform/showpartial", @personlist
%>
> 
> > The partials also share the entire instance variables ( e.g.
> > everything starting with @ ) with the main template.
> 
> Ok, but for my specific case I need to access the passed variables under a
> name independent from the name that was passed.
> 
> (Oh man, I barely understand it myself when I read all that, I hope you can
> make something out of it ;-) )
> 
> 
> 
> Regards,
> Sebastian
> 
> --
> PGP-Key: http://www.mmweg.rwth-aachen.de/~sebastian.ley/public.key
> Fingerprint: A46A 753F AEDC 2C01 BE6E  F6DB 97E0 3309 9FD6 E3E6
> 
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
> 

-- 
Tobi

* Tobias Luetke wrote:
> file: app/view/test/_test.rhtml :
> <%= test %>
Okay, here was my mistake, I used <%= _test %>. Now i works, thanks for
your
help!
> If you have any other problems you should come to IRC, I can help you
> there directly ( in german, too )
I am (Wile_E) and will bother you again soon I suppose ;-)

Regards,
Sebastian


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