+++ /dev/null
-=head1 NAME
-
-Catalyst::Manual::Tutorial::Debugging - Catalyst Tutorial - Part 6: Debugging
-
-=head1 OVERVIEW
-
-This is B<Part 6 of 9> for the Catalyst tutorial.
-
-L<Tutorial Overview|Catalyst::Manual::Tutorial>
-
-=over 4
-
-=item 1
-
-L<Introduction|Catalyst::Manual::Tutorial::Intro>
-
-=item 2
-
-L<Catalyst Basics|Catalyst::Manual::Tutorial::CatalystBasics>
-
-=item 3
-
-L<Basic CRUD|Catalyst::Manual::Tutorial_BasicCRUD>
-
-=item 4
-
-L<Authentication|Catalyst::Manual::Tutorial::Authentication>
-
-=item 5
-
-L<Authorization|Catalyst::Manual::Tutorial::Authorization>
-
-=item 6
-
-B<Debugging>
-
-=item 7
-
-L<Testing|Catalyst::Manual::Tutorial::Testing>
-
-=item 8
-
-L<AdvancedCRUD|Catalyst::Manual::Tutorial::AdvancedCRUD>
-
-=item 9
-
-L<Appendices|Catalyst::Manual::Tutorial::Appendices>
-
-=back
-
-
-=head1 DESCRIPTION
-
-This part of the tutorial takes a brief look at the primary options
-available for troubleshooting Catalyst applications.
-
-Note that when it comes to debugging and troubleshooting, there are two
-camps:
-
-=over 4
-
-=item *
-
-Fans of C<log> and C<print> statements embedded in the code.
-
-=item *
-
-Fans of interactive debuggers.
-
-=back
-
-Catalyst is able to easily accommodate both styles of debugging.
-
-=head1 LOG STATEMENTS
-
-Folks in the former group can use Catalyst's C<$c-E<gt>log> facility.
-(See L<Catalyst::Log> for more detail.) For example, if you add the
-following code to a controller action method:
-
- $c->log->info("Starting the foreach loop here");
-
- $c->log->debug("Value of $id is: ".$id);
-
-Then the Catalyst development server will display your message along
-with the other debug output. To accomplish the same thing in a TTSite
-view use:
-
- [% Catalyst.log.debug("This is a test log message") %]
-
-You can also use L<Data::Dumper|Data::Dumper> in both Catalyst code
-(C<use Data::Dumper; $c-E<gt>log-E<gt>debug("$var is: ".Dumper($var));)>)
-and TT templates (C<[% Dumper.dump(book) %]>.
-
-=head1 RUNNING CATALYST UNDER THE PERL DEBUGGER
-
-Members of the interactive-debugger fan club will also be at home with
-Catalyst applications. One approach to this style of Perl debugging is
-to embed breakpoints in your code. For example, open
-C<lib/MyApp/Controller/Books.pm> in your editor and add the
-C<DB::single=1> line as follows inside the C<list> method (I like to
-"left-justify" my debug statements so I don't forget to remove them, but
-you can obviously indent them if you prefer):
-
- sub list : Local {
- # Retrieve the usual perl OO '$self' for this object. $c is the Catalyst
- # 'Context' that's used to 'glue together' the various components
- # that make up the application
- my ($self, $c) = @_;
-
- $DB::single=1;
-
- # Retrieve all of the book records as book model objects and store in the
- # stash where they can be accessed by the TT template
- $c->stash->{books} = [$c->model('MyAppDB::Book')->all];
-
- # Set the TT template to use. You will almost always want to do this
- # in your action methods.
- $c->stash->{template} = 'books/list.tt2';
- }
-
-This causes the Perl Debugger to enter "single step mode" when this command is
-encountered (it has no effect when Perl is run without the C<-d> flag).
-
-To now run the Catalyst development server under the Perl debugger, simply
-prepend C<perl -d> to the front of C<script/myapp_server.pl>:
-
- $ perl -d script/myapp_server.pl
-
-This will start the interactive debugger and produce output similar to:
-
- $ perl -d script/myapp_server.pl
-
- Loading DB routines from perl5db.pl version 1.27
- Editor support available.
-
- Enter h or `h h' for help, or `man perldebug' for more help.
-
- main::(script/myapp_server.pl:14): my $debug = 0;
-
- DB<1>
-
-Press the C<c> key and hit C<Enter> to continue executing the Catalyst
-development server under the debugger. Although execution speed will be
-slightly slower than normal, you should soon see the usual Catalyst
-startup debug information.
-
-Now point your browser to L<http://localhost:3000/books/list> and log
-in. Once the breakpoint is encountered in the
-C<MyApp::Controller::list> method, the console session running the
-development server will drop to the Perl debugger prompt:
-
- MyApp::Controller::Books::list(/home/me/MyApp/script/../lib/MyApp/Controller/Books.pm:40):
- 40: $c->stash->{books} = [$c->model('MyAppDB::Book')->all];
-
- DB<1>
-
-You now have the full Perl debugger at your disposal. First use the
-C<next> feature by typing C<n> to execute the C<all> method on the Book
-model (C<n> jumps over method/subroutine calls; you can also use C<s> to
-C<single-step> into methods/subroutines):
-
- DB<1> n
- SELECT me.id, me.authors, me.title, me.rating FROM books me:
- MyApp::Controller::Books::list(/home/me/MyApp/script/../lib/MyApp/Controller/Books.pm:44):
- 44: $c->stash->{template} = 'books/list.tt2';
-
- DB<1>
-
-This takes you to the next line of code where the template name is set.
-Notice that because we enabled C<DBIC_TRACE=1> earlier, SQL debug
-output also shows up in the development server debug information.
-
-Next, list the methods available on our C<Book> model:
-
- DB<1> m $c->model('MyAppDB::Book')
- ()
- (0+
- (bool
- MODIFY_CODE_ATTRIBUTES
- _attr_cache
- _collapse_result
- _construct_object
- _count
- _result_class_accessor
- _result_source_accessor
- all
- carp
- <lines removed for brevity>
-
- DB<2>
-
-We can also play with the model directly:
-
- DB<2> x ($c->model('MyAppDB::Book')->all)[1]->title
- SELECT me.id, me.title, me.rating FROM books me:
- 0 'TCP/IP Illustrated, Volume 1'
-
-This uses the Perl debugger C<x> command to display the title of a book.
-
-Next we inspect the C<books> element of the Catalyst C<stash> (the C<4>
-argument to the C<x> command limits the depth of the dump to 4 levels):
-
- DB<3> x 4 $c->stash->{books}
- 0 ARRAY(0xa8f3b7c)
- 0 MyApp::Model::MyAppDB::Book=HASH(0xb8e702c)
- '_column_data' => HASH(0xb8e5e2c)
- 'id' => 1
- 'rating' => 5
- 'title' => 'CCSP SNRS Exam Certification Guide'
- '_in_storage' => 1
- <lines removed for brevity>
-
-Then enter the C<c> command to continue processing until the next
-breakpoint is hit (or the application exits):
-
- DB<4> c
- SELECT author.id, author.first_name, author.last_name FROM ...
-
-Finally, press C<Ctrl+C> to break out of the development server.
-Because we are running inside the Perl debugger, you will drop to the
-debugger prompt. Press C<q> to exit the debugger and return to your OS
-shell prompt:
-
- DB<4> q
- $
-
-For more information on using the Perl debugger, please see C<perldebug>
-and C<perldebtut>. You can also type C<h> or C<h h> at the debugger
-prompt to view the built-in help screens.
-
-
-=head1 DEBUGGING MODULES FROM CPAN
-
-Although the techniques discussed above work well for code you are
-writing, what if you want to use print/log/warn messages or set
-breakpoints in code that you have installed from CPAN (or in module that
-ship with Perl)? One helpful approach is to place a copy of the module
-inside the C<lib> directory of your Catalyst project. When Catalyst
-loads, it will load from inside your C<lib> directory first, only
-turning to the global modules if a local copy cannot be found. You can
-then make modifications such as adding a C<$DB::single=1> to the local
-copy of the module without risking the copy in the original location.
-This can also be a great way to "locally override" bugs in modules while
-you wait for a fix on CPAN.
-
-
-Matt Trout has suggested the following shortcut to create a local
-copy of an installed module:
-
- mkdir -p lib/Module; cp `perldoc -l Module::Name` lib/Module/
-
-For example, you could make a copy of
-L<Catalyst::Plugin::Authentication|Catalyst::Plugin::Authentication>
-with the following command:
-
- mkdir -p lib/Catalyst/Plugin; cp \
- `perldoc -l Catalyst::Plugin::Authentication` lib/Catalyst/Plugin
-
-B<Note:> Matt has also suggested the following tips for Perl
-debugging:
-
-=over 4
-
-=item *
-
-Check the version of an installed module:
-
- perl -MModule::Name -e 'print $Module::Name::VERSION;'
-
-For example:
-
- $ perl -MCatalyst::Plugin::Authentication -e \
- 'print $Catalyst::Plugin::Authentication::VERSION;'
- 0.07
-
-=item *
-
-Check if a modules contains a given method:
-
- perl -MModule::Name -e 'print Module::Name->can("method");'
-
-For example:
-
- $ perl -MCatalyst::Plugin::Authentication -e \
- 'print Catalyst::Plugin::Authentication->can("prepare");'
- CODE(0x9c8db2c)
-
-If the method exists, the Perl C<can> method returns a coderef.
-Otherwise, it returns undef and nothing will be printed.
-
-=back
-
-
-=head1 AUTHOR
-
-Kennedy Clark, C<hkclark@gmail.com>
-
-Please report any errors, issues or suggestions to the author. The
-most recent version of the Catalyst Tutorial can be found at
-L<http://dev.catalyst.perl.org/repos/Catalyst/trunk/Catalyst-Runtime/lib/Catalyst/Manual/Tutorial/>.
-
-Copyright 2006, Kennedy Clark, under Creative Commons License
-(L<http://creativecommons.org/licenses/by-nc-sa/2.5/>).
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