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Steve Litt

2006-Jan-06 21:54 UTC

[Rails] I need debugging tips?

Hi all,

Like most other frameworks, Ruby groups code by Model/View/Controller instead 
of by task, and therefore I''m having a hard time debugging a problem
from the
Agile Rails book where looping through @items errors out because one or more 
items is nil.

I managed to empty the cart by placing session[:cart] = nil in find_cart() in 
the store_controller_rb, and the problem continued after I removed that 
diagnostic, thereby proving it wasn''t caused just a bad record that got
in
there. I''ve examined the dump screen produced by the error every way
but
loose and can''t find anything that helps. I went back and looked at 
everything I did recently -- nothing obvious. I looked at log/production.log, 
and saw an error pointing to code I didn''t write (Rails code, in other 
words).

I''d like to place diagnostic prints in the controller code to see if
I''m
placing nil records in the @items whatever, but where would such diagnostic 
prints print out?

So I need some debugging tips. What are your favorite Rails debugging 
techniques?

Thanks

SteveT

Steve Litt
Author: 
   * Universal Troubleshooting Process courseware
   * Troubleshooting Techniques of the Successful Technologist
   * Rapid Learning: Secret Weapon of the Successful Technologist
Webmaster
   * Troubleshooters.Com
   * http://www.troubleshooters.com

Bakki Kudva

2006-Jan-06 22:04 UTC

head link

[Rails] I need debugging tips?

I like to use breakpoints in the code and invoke script/breakpointer. It
drops me into irb and ALL the environment vars of the controller are
available. You can ctrl-D to continue and if your breakpoint() is in a loop
you will hit it each time and see the vars changing.

-bakki kudva

On 1/6/06, Steve Litt <slitt@troubleshooters.com> wrote:
...
> I''d like to place diagnostic prints in the controller code to see
if I''m
> placing nil records in the @items whatever, but where would such
> diagnostic
> prints print out?
>
> So I need some debugging tips. What are your favorite Rails debugging
> techniques?
>
> Thanks
>
> SteveT
>
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
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Ezra Zygmuntowicz

2006-Jan-06 22:13 UTC

head link

[Rails] I need debugging tips?

On Jan 6, 2006, at 1:56 PM, Steve Litt wrote:
> Hi all,
>
> Like most other frameworks, Ruby groups code by Model/View/ 
> Controller instead
> of by task, and therefore I''m having a hard time debugging a  
> problem from the
> Agile Rails book where looping through @items errors out because  
> one or more
> items is nil.
>
> I managed to empty the cart by placing session[:cart] = nil in  
> find_cart() in
> the store_controller_rb, and the problem continued after I removed  
> that
> diagnostic, thereby proving it wasn''t caused just a bad record
that
> got in
> there. I''ve examined the dump screen produced by the error every  
> way but
> loose and can''t find anything that helps. I went back and looked
at
> everything I did recently -- nothing obvious. I looked at log/ 
> production.log,
> and saw an error pointing to code I didn''t write (Rails code, in
other
> words).
>
> I''d like to place diagnostic prints in the controller code to see
> if I''m
> placing nil records in the @items whatever, but where would such  
> diagnostic
> prints print out?
>
> So I need some debugging tips. What are your favorite Rails debugging
> techniques?
>
> Thanks
>
> SteveT
Steve-

	One good way to debug nil errors in your views is to use the debug  
method. So if your looping over @items try this at the top of your view:

<%= debig(@items) %>

	You will get a pretty printed yaml version of your object and all  
the data it holds. And another way to avoid the nil errors inside of  
a loop is to do something like this:

<% @items.each do |item| -%>
    <p><%= item.name rescue nil -%></p>
    <p><%= item.info rescue nil -%></p>
<% end -%>

	The rescue nil deal will just print an empty string instead of  
making your whole page error out with a nil error when item.whatever  
is nil inside the loop. Hope that helps a bit.

Cheers-
-Ezra Zygmuntowicz
Yakima Herald-Republic
WebMaster
http://yakimaherald.com
509-577-7732
ezra@yakima-herald.com

Steve Litt

2006-Jan-06 23:11 UTC

head link

[Rails] I need debugging tips?

On Friday 06 January 2006 05:04 pm, Bakki Kudva wrote:> I like to use breakpoints in the code and invoke script/breakpointer. It
> drops me into irb and ALL the environment vars of the controller are
> available. You can ctrl-D to continue and if your breakpoint() is in a loop
> you will hit it each time and see the vars changing.
>
> -bakki kudva
Sounds good Bakki,

How do I set a breakpoint?

Thanks

SteveT
> On 1/6/06, Steve Litt <slitt@troubleshooters.com> wrote:
> ...
>
> > I''d like to place diagnostic prints in the controller code to
see if I''m
> > placing nil records in the @items whatever, but where would such
> > diagnostic
> > prints print out?
> >
> > So I need some debugging tips. What are your favorite Rails debugging
> > techniques?
> >
> > Thanks
> >
> > SteveT
> >
> > _______________________________________________
> > Rails mailing list
> > Rails@lists.rubyonrails.org
> > http://lists.rubyonrails.org/mailman/listinfo/rails

Tom Fakes

2006-Jan-06 23:18 UTC

head link

[Rails] I need debugging tips?

No-one''s mentioned logging yet.

In a controller, you can write this:

	logger.info "My Stuff: #(@items.inspect)"

And this output shows up in the log/development.log file.

The logging functionality is more important to me than the IRB solution, as
I can leave it in the code and check the log output if I seem something
break.

More info here:
http://wiki.rubyonrails.com/rails/pages/HowtoConfigureLogging
http://wiki.rubyonrails.com/rails/pages/logger


-----Original Message-----
From: rails-bounces@lists.rubyonrails.org
[mailto:rails-bounces@lists.rubyonrails.org] On Behalf Of Steve Litt
Sent: Friday, January 06, 2006 3:13 PM
To: rails@lists.rubyonrails.org
Subject: Re: [Rails] I need debugging tips?

On Friday 06 January 2006 05:04 pm, Bakki Kudva wrote:> I like to use breakpoints in the code and invoke script/breakpointer. It
> drops me into irb and ALL the environment vars of the controller are
> available. You can ctrl-D to continue and if your breakpoint() is in a
loop> you will hit it each time and see the vars changing.
>
> -bakki kudva
Sounds good Bakki,

How do I set a breakpoint?

Thanks

SteveT
> On 1/6/06, Steve Litt <slitt@troubleshooters.com> wrote:
> ...
>
> > I''d like to place diagnostic prints in the controller code to
see if I''m
> > placing nil records in the @items whatever, but where would such
> > diagnostic
> > prints print out?
> >
> > So I need some debugging tips. What are your favorite Rails debugging
> > techniques?
> >
> > Thanks
> >
> > SteveT
> >
> > _______________________________________________
> > Rails mailing list
> > Rails@lists.rubyonrails.org
> > http://lists.rubyonrails.org/mailman/listinfo/rails_______________________________________________
Rails mailing list
Rails@lists.rubyonrails.org
http://lists.rubyonrails.org/mailman/listinfo/rails

Steve Litt

2006-Jan-06 23:37 UTC

head link

[Rails] I need debugging tips?

On Friday 06 January 2006 06:19 pm, Tom Fakes wrote:> No-one''s mentioned logging yet.
>
> In a controller, you can write this:
>
> 	logger.info "My Stuff: #(@items.inspect)"
>
> And this output shows up in the log/development.log file.
>
> The logging functionality is more important to me than the IRB solution, as
> I can leave it in the code and check the log output if I seem something
> break.
>
> More info here:
> http://wiki.rubyonrails.com/rails/pages/HowtoConfigureLogging
> http://wiki.rubyonrails.com/rails/pages/logger
Oh Oh,

undefined local variable or method `logger'' for
#<Cart:0x407f5e2c>

This happened before and after I added the following to the bottom of 
config/environment.rb:

begin
  RAILS_DEFAULT_LOGGER =
Logger.new("#{RAILS_ROOT}/log/#{RAILS_ENV}.log")
rescue StandardError
  RAILS_DEFAULT_LOGGER = Logger.new(STDERR)
  RAILS_DEFAULT_LOGGER.level = Logger::WARN
  RAILS_DEFAULT_LOGGER.warn(
    "Rails Error: Unable to access log file. Please ensure that 
log/#{RAILS_ENV}.log exists and is chmod 0666. " +
    "The log level has been raised to WARN and the output directed to
STDERR
until the problem is fixed." 
  )
end
[ActiveRecord, ActionController, ActionMailer].each { |mod| mod::Base.logger 
||= RAILS_DEFAULT_LOGGER }

Steve Litt

2006-Jan-06 23:44 UTC

head link

[Rails] I need debugging tips?

On Friday 06 January 2006 05:10 pm, Ezra Zygmuntowicz wrote:
> Steve-
>
> 	One good way to debug nil errors in your views is to use the debug
> method. So if your looping over @items try this at the top of your view:
>
> <%= debig(@items) %>
>
> 	You will get a pretty printed yaml version of your object and all
> the data it holds. 
I tried that and didn''t see any nils, unless the dash at the bottom,
with
nothing after it, indicates a nil. Does that lone dash indicate a nil?

Thanks

Steve

Tom Fakes

2006-Jan-07 00:12 UTC

head link

[Rails] I need debugging tips?

The logger variable is part of your controller.  Your original question was:

"I''d like to place diagnostic prints in the controller code to see
if I''m
placing nil records in the @items whatever, but where would such diagnostic
prints print out?"

So, this will work:
class MyController < ApplicationController
	def some_action
		logger.info "My Cart Is: #{@cart.inspect}"
	end
end


But your current problem is that you are trying to log from a Model object
that is not derived from the ActiveRecord::Base class.  In that case you
have to do use the RAILS_DEFAULT_LOGGER global constant:

class Cart
	def something
		RAILS_DEFAULT_LOGGER.info "My Cart Is: #{self.inspect}"
	end
end


If you are using Rails 1.0, the code you added to environment.rb is not
necessary, it is built into Rails.

-----Original Message-----
From: rails-bounces@lists.rubyonrails.org
[mailto:rails-bounces@lists.rubyonrails.org] On Behalf Of Steve Litt
Sent: Friday, January 06, 2006 3:40 PM
To: rails@lists.rubyonrails.org
Subject: Re: [Rails] I need debugging tips?

On Friday 06 January 2006 06:19 pm, Tom Fakes wrote:> No-one''s mentioned logging yet.
>
> In a controller, you can write this:
>
> 	logger.info "My Stuff: #(@items.inspect)"
>
> And this output shows up in the log/development.log file.
>
> The logging functionality is more important to me than the IRB solution,
as> I can leave it in the code and check the log output if I seem something
> break.
>
> More info here:
> http://wiki.rubyonrails.com/rails/pages/HowtoConfigureLogging
> http://wiki.rubyonrails.com/rails/pages/logger
Oh Oh,

undefined local variable or method `logger'' for
#<Cart:0x407f5e2c>

This happened before and after I added the following to the bottom of 
config/environment.rb:

begin
  RAILS_DEFAULT_LOGGER =
Logger.new("#{RAILS_ROOT}/log/#{RAILS_ENV}.log")
rescue StandardError
  RAILS_DEFAULT_LOGGER = Logger.new(STDERR)
  RAILS_DEFAULT_LOGGER.level = Logger::WARN
  RAILS_DEFAULT_LOGGER.warn(
    "Rails Error: Unable to access log file. Please ensure that 
log/#{RAILS_ENV}.log exists and is chmod 0666. " +
    "The log level has been raised to WARN and the output directed to
STDERR

until the problem is fixed." 
  )
end
[ActiveRecord, ActionController, ActionMailer].each { |mod| mod::Base.logger

||= RAILS_DEFAULT_LOGGER }
_______________________________________________
Rails mailing list
Rails@lists.rubyonrails.org
http://lists.rubyonrails.org/mailman/listinfo/rails

Ezra Zygmuntowicz

2006-Jan-07 00:47 UTC

head link

[Rails] I need debugging tips?

On Jan 6, 2006, at 3:46 PM, Steve Litt wrote:
> On Friday 06 January 2006 05:10 pm, Ezra Zygmuntowicz wrote:
>
>> Steve-
>>
>> 	One good way to debug nil errors in your views is to use the debug
>> method. So if your looping over @items try this at the top of your  
>> view:
>>
>> <%= debig(@items) %>
>>
>> 	You will get a pretty printed yaml version of your object and all
>> the data it holds.
>
> I tried that and didn''t see any nils, unless the dash at the  
> bottom, with
> nothing after it, indicates a nil. Does that lone dash indicate a nil?
>
> Thanks
>
> Steve

I think it does, but could you paste the debug yaml dump here and I  
can tell you?

Cheers-
-Ezra Zygmuntowicz
WebMaster
Yakima Herald-Republic Newspaper
ezra@yakima-herald.com
509-577-7732

Bakki Kudva

2006-Jan-07 21:46 UTC

head link

[Rails] I need debugging tips?

Just insert breakpoint() in your ruby code which you want to examine.
Invoke script/breakpointer and you should see..
No connection to breakpoint service at
druby://localhost:42531(DRb::DRbConnError)
Tries to connect will be made every 2 seconds...
Don''t worry about the ''No connection at breakpoint''
bit. Carry on with your
app and when the breakpoint hits you will see something like:
Executing break point at
./script/../config/../app/controllers/my_controller.rb:16 in `new''
irb(#<MyController:0x4079fef0>):001:0>
Which means you are in irb. Now you can simply type in variable names and
look at their values.
The best documentation I found for the breakpointer is in its source file
which is at:
/usr/lib/ruby/gems/1.8/gems/activesupport-1.2.5/lib/active_support/breakpoint.rb
on my Debian system.

hope it helps,

bakki

On 1/6/06, Steve Litt <slitt@troubleshooters.com>
wrote:>
> On Friday 06 January 2006 05:04 pm, Bakki Kudva wrote:
> > I like to use breakpoints in the code and invoke script/breakpointer.
It
> > drops me into irb and ALL the environment vars of the controller are
> > available. You can ctrl-D to continue and if your breakpoint() is in a
> loop
> > you will hit it each time and see the vars changing.
> >
> > -bakki kudva
>
> Sounds good Bakki,
>
> How do I set a breakpoint?
>
> Thanks
>
> SteveT
>
> > On 1/6/06, Steve Litt <slitt@troubleshooters.com> wrote:
> > ...
> >
> > > I''d like to place diagnostic prints in the controller
code to see if
> I''m
> > > placing nil records in the @items whatever, but where would such
> > > diagnostic
> > > prints print out?
> > >
> > > So I need some debugging tips. What are your favorite Rails
debugging
> > > techniques?
> > >
> > > Thanks
> > >
> > > SteveT
> > >
> > > _______________________________________________
> > > Rails mailing list
> > > Rails@lists.rubyonrails.org
> > > http://lists.rubyonrails.org/mailman/listinfo/rails
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
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Vivek Krishna

2006-Jan-09 04:11 UTC

head link

[Rails] I need debugging tips?

How does one single step through the code? I have tried irb and it doenst
allow me to do that!

On 1/7/06, Steve Litt <slitt@troubleshooters.com>
wrote:>
> On Friday 06 January 2006 05:10 pm, Ezra Zygmuntowicz wrote:
>
> > Steve-
> >
> >       One good way to debug nil errors in your views is to use the
debug
> > method. So if your looping over @items try this at the top of your
view:
> >
> > <%= debig(@items) %>
> >
> >       You will get a pretty printed yaml version of your object and
all
> > the data it holds.
>
> I tried that and didn''t see any nils, unless the dash at the
bottom, with
> nothing after it, indicates a nil. Does that lone dash indicate a nil?
>
> Thanks
>
> Steve
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
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