From: Kennedy Clark <hkclark@gmail.com>
Date: Thu, 5 Mar 2009 17:57:54 +0000 (+0000)
Subject: Add a new section to BasicCRUD covering more advanced features of DBIC ("EXPLORING... 
X-Git-Tag: v5.8005~192
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?p=catagits%2FCatalyst-Manual.git;a=commitdiff_plain;h=1cde0fd603f0f21f0197632bd19904f468f28c83

Add a new section to BasicCRUD covering more advanced features of DBIC ("EXPLORING THE POWER OF DBIC") plus a few other minor changes
---

diff --git a/Changes b/Changes
index b00cf9d..5153988 100644
--- a/Changes
+++ b/Changes
@@ -1,5 +1,9 @@
 Revision history for Catalyst-Manual
 
+5.7XXX  XXXXXX
+        - Add a new section to BasicCRUD covering more advanced features of 
+            DBIC ("EXPLORING THE POWER OF DBIC")
+
 5.7018  2 Mar 2009
         - Suggestions and fixes with thanks to mintywalker@gmail.com
         - DBIC-related updates in MoreCatalystBasics
diff --git a/lib/Catalyst/Manual/Tutorial/Appendices.pod b/lib/Catalyst/Manual/Tutorial/Appendices.pod
index 2195e63..c8037df 100644
--- a/lib/Catalyst/Manual/Tutorial/Appendices.pod
+++ b/lib/Catalyst/Manual/Tutorial/Appendices.pod
@@ -321,7 +321,8 @@ Delete the existing model:
 
 Regenerate the model using the Catalyst "_create.pl" script:
 
-    script/myapp_create.pl model MyAppDB DBIC::Schema MyApp::Schema dbi:mysql:myapp 'tutorial' '' '{ AutoCommit => 1 }'
+    script/myapp_create.pl model MyAppDB DBIC::Schema MyApp::Schema \
+        dbi:mysql:myapp '_username_here_' '_password_here_' '{ AutoCommit => 1 }'
 
 =back
 
diff --git a/lib/Catalyst/Manual/Tutorial/BasicCRUD.pod b/lib/Catalyst/Manual/Tutorial/BasicCRUD.pod
index 6a8278f..598f3e2 100644
--- a/lib/Catalyst/Manual/Tutorial/BasicCRUD.pod
+++ b/lib/Catalyst/Manual/Tutorial/BasicCRUD.pod
@@ -407,14 +407,14 @@ method:
     sub base :Chained('/') :PathPart('books') :CaptureArgs(0) {
         my ($self, $c) = @_;
         
-        # Store the resultset in stash so it's available for other methods
+        # Store the ResultSet in stash so it's available for other methods
         $c->stash->{resultset} = $c->model('DB::Books');
     
         # Print a message to the debug log
         $c->log->debug('*** INSIDE BASE METHOD ***');
     }
 
-Here we print a log message and store the DBIC resultset in 
+Here we print a log message and store the DBIC ResultSet in 
 C<$c-E<gt>stash-E<gt>{resultset}> so that it's automatically available 
 for other actions that chain off C<base>.  If your controller always 
 needs a book ID as it's first argument, you could have the base method 
@@ -585,7 +585,7 @@ from the database.
 
 =head2 Include a Delete Link in the List
 
-Edit C<root/src/books/list.tt2> and update it to the following (two
+Edit C<root/src/books/list.tt2> and update it to match the following (two
 sections have changed: 1) the additional '<th>Links</th>' table header,
 and 2) the four lines for the Delete link near the bottom).
 
@@ -928,6 +928,461 @@ that should really go to Window A.  For this reason, you may wish
 to use the "query param" technique shown here in your applications.
 
 
+=head1 EXPLORING THE POWER OF DBIC
+
+In this section we will explore some additional capabilities offered 
+by DBIx::Class.  Although these features have relatively little to do 
+with Catalyst per-se, you will almost certainly want to take advantage 
+of them in your applications.
+
+
+=head2 Convert to DBIC "load_namespaces"
+
+If you look back at 
+L<Catalyst::Manual::Tutorial::MoreCatalystBasics/Create Static DBIC 
+Schema Files> you will recall that we load our DBIC Result Classes 
+(Books.pm, Authors.pm and BookAuthors.pm) with  in 
+C<lib/MyApp/Schema.pm> with the C<load_classes> feature.  Although 
+this method is perfectly valid, the DBIC community has migrated to a 
+newer C<load_namespaces> technique because it more easily supports a 
+variety of advanced features.  Since we want to explore some of these 
+features below, let's first migrate our configuration over to use 
+C<load_namespaces>.
+
+If you are following along in Ubuntu 8.10, you will need to
+upgrade your version of 
+L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema>
+to 0.22 or higher.  To do this, we can install directly from CPAN:
+
+    $ cpan Catalyst::Model::DBIC::Schema
+
+Then make sure you are running an appropriate version:
+
+    $ perl -MCatalyst::Model::DBIC::Schema -e \
+        'print "$Catalyst::Model::DBIC::Schema::VERSION\n"'
+    0.22
+
+Make sure you get version 0.22 or higher.
+
+B<Note:> Utuntu will automatically "do the right thing" and use the 
+module we installed from CPAN and ignore the older version we picked 
+up via the C<apt-get> command.  If you are using a different 
+environment, you will need to make sure you are using v0.22 or higher 
+with the command above.
+
+While we are at it, let's install a few other modules from CPAN for 
+some of the other work we will be doing below:
+
+    $ cpan Time::Warp DBICx::TestDatabase \
+        DBIx::Class::DynamicDefault DBIx::Class::TimeStamp
+
+Next, we need to delete the existing C<lib/MyApp/Schema.pm> so that
+the Catalyst DBIC helper will recreate it.  Then we re-generate
+the model and schema information:
+
+    $ rm lib/MyApp/Schema.pm
+    $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
+        create=static components=TimeStamp dbi:SQLite:myapp.db
+     exists "/root/dev/MyApp/script/../lib/MyApp/Model"
+     exists "/root/dev/MyApp/script/../t"
+    Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ...
+    Schema dump completed.
+     exists "/root/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
+    $
+    $ ls lib/MyApp/Schema
+    Authors.pm  BookAuthors.pm  Books.pm  Result
+    $ ls lib/MyApp/Schema/Result
+    Authors.pm  BookAuthors.pm  Books.pm
+
+Notice that we now have a duplicate set of Result Class files.  With 
+the newer C<load_namespaces> feature, DBIC automatically looks for 
+your Result Class files in a subdirectory of the Schema directory 
+called C<Result> (the files in C<lib/MyApp/Schema> were already there 
+from Part 3 of the tutorial; the files in C<lib/MyApp/Schema/Result> 
+are new).  
+
+If you are using SQLite, you will need to manually re-enter the 
+relationship configuration as we did in Part 3 of the tutorial (if you 
+are using different database, the relationships might have been auto-
+generated by Schema::Loader).  One option is to use the following 
+command-line perl script to migrate the information across 
+automatically:
+
+    $ cd lib/MyApp/Schema
+    $ perl -MIO::All -e 'for (@ARGV) { my $s < io($_); $s =~ s/.*\n\# You can replace.*?\n//s; 
+          $s =~ s/'MyApp::Schema::/'MyApp::Schema::Result::/g; my $d < io("Result/$_"); 
+          $d =~ s/1;\n?//; "$d$s" > io("Result/$_"); }' *.pm
+    $ cd ../../..
+
+If you prefer, you can do the migration by hand using "cut and paste" 
+from the files in C<lib/MyApp/Schema> (or from 
+L<Catalyst::Manual::Tutorial::MoreCatalystBasics/Updating the Generated DBIC Schema Files>) 
+to the corresponding files in C<lib/MyApp/Schema/Result>.  If you take 
+this approach, be sure to add C<::Result> to the end of 
+C<MyApp::Schema> in all three files (for example, in C<Books.pm>, the 
+"peer class" in the C<has_many> relationship needs to be changed from 
+C<MyApp::Schema::BookAuthors> to C<MyApp::Schema::BookAuthors::Result>).
+
+Now we can remove the original set of Result Class files that we no 
+longer need:
+
+    $ rm lib/MyApp/Schema/*.pm
+    $ ls lib/MyApp/Schema
+    Result
+
+Finally, test the application to be sure everything is still 
+working under our new configuration.  Use the 
+C<script/myapp_server.pl> command to start the development server and 
+point your browser to L<http://localhost:3000/books/list>.  Make sure 
+you see the existing list of books.
+
+
+=head2 Add Datetime Columns to Our Existing Books Table
+
+Let's add two columns to our existing C<books> table to track when 
+each book was added and when each book is updated:
+
+    $ sqlite3 myapp.db
+    sqlite> ALTER TABLE books ADD created INTEGER;
+    sqlite> ALTER TABLE books ADD updated INTEGER;
+    sqlite> UPDATE books SET created = DATETIME('NOW'), updated = DATETIME('NOW');
+    sqlite> SELECT * FROM books;
+    1|CCSP SNRS Exam Certification Guide|5|2009-03-03 07:31:32|2009-03-03 07:31:32
+    2|TCP/IP Illustrated, Volume 1|5|2009-03-03 07:31:32|2009-03-03 07:31:32
+    ...
+    sqlite> .quit
+    $
+
+This will modify the C<books> table to include the two new fields
+and populate those fields with the current time.
+
+=head2 Update DBIC to Automatically Handle the Datetime Columns
+
+Next, we should re-run the DBIC helper to update the Result Classes
+with the new fields:
+
+    $ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
+        create=static components=TimeStamp dbi:SQLite:myapp.db
+     exists "/root/dev/MyApp/script/../lib/MyApp/Model"
+     exists "/root/dev/MyApp/script/../t"
+    Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ...
+    Schema dump completed.
+     exists "/root/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
+
+Notice that we modified our use of the helper slightly: we told
+it to include the L<DBIx::Class::Timestamp|DBIx::Class::Timestamp>
+in the C<load_components> line of the Result Classes.
+
+If you open C<lib/MyApp/Schema/Result/Books.pm> in your editor you 
+should see that the C<created> and C<updated> fields are now included 
+in the call to add_columns(), but our relationship information below 
+the "C<# DO NOT MODIFY...>" line was automatically preserved.  
+
+While we have this file open, let's update it with some additional 
+information to have DBIC automatically handle the updating of these 
+two fields for us.  Insert the following code at the bottom of the 
+file (it B<must> be B<below> the "C<# DO NOT MODIFY...>" line and 
+B<above> the C<1;> on the last line):
+
+    #
+    # Enable automatic date handling
+    #
+    __PACKAGE__->add_columns(
+        "created",
+        { data_type => 'datetime', set_on_create => 1 },
+        "updated",
+        { data_type => 'datetime', set_on_create => 1, set_on_update => 1 },
+    );      
+
+This will override the definition for these fields that Schema::Loader 
+placed at the top of the file.  The C<set_on_create> and 
+C<set_on_update> options will cause DBIC to automatically update the 
+timestamps in these columns whenever a row is created or modified.
+
+To test this out, restart the development server using the
+C<DBIC_TRACE=1> option:
+
+    DBIC_TRACE=1 script/myapp_server.pl
+
+Then enter the following URL into your web browser:
+
+    http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
+
+You should get the same "Book Created" screen we saw above.  However,
+if you now use the sqlite3 command-line tool to dump the C<books> table,
+you will see that the new book we added has an appropriate date and
+time entered for it (see the last line in the listing below):
+
+    sqlite3 myapp.db "select * from books"
+    1|CCSP SNRS Exam Certification Guide|5|2009-03-05 17:18:53|2009-03-05 17:18:53
+    2|TCP/IP Illustrated, Volume 1|5|2009-03-05 17:18:53|2009-03-05 17:18:53
+    3|Internetworking with TCP/IP Vol.1|4|2009-03-05 17:18:53|2009-03-05 17:18:53
+    4|Perl Cookbook|5|2009-03-05 17:18:53|2009-03-05 17:18:53
+    5|Designing with Web Standards|5|2009-03-05 17:18:53|2009-03-05 17:18:53
+    9|TCP/IP Illustrated, Vol 3|5|2009-03-05 17:18:53|2009-03-05 17:18:53
+    10|TCPIP_Illustrated_Vol-2|5|2009-03-05 17:24:18|2009-03-05 17:24:18
+
+Notice in the debug log that the SQL DBIC generated has changed to 
+incorporate the datetime logic:
+
+    INSERT INTO books (created, rating, title, updated) VALUES (?, ?, ?, ?): 
+    '2009-03-05 17:24:18', '5', 'TCPIP_Illustrated_Vol-2', '2009-03-05 17:24:18'
+    INSERT INTO book_authors (author_id, book_id) VALUES (?, ?): '4', '10'
+
+
+=head2 Create a ResultSet Class
+
+An often overlooked but extremly powerful features of DBIC is that it 
+allows you to supply your own subclasses of C<DBIx::Class::ResultSet>. 
+It allows you to pull complex and unsightly "query code" out of your 
+controllers and encapsulate it in a method of your ResultSet Class.
+These "canned queries" in your ResultSet Class can then be invoked
+via a single call, resulting in much cleaner and easier to read
+controller code.
+
+To illustrate the concept with a fairly simple example, let's create a 
+method that returns books added in the last 10 minutes.  Start by
+making a directory where DBIC will look for our ResultSet Class:
+
+    mkdir lib/MyApp/Schema/ResultSet
+
+Then open C<lib/MyApp/Schema/ResultSet/Books.pm> and enter the following: 
+
+    package MyApp::Schema::ResultSet::Books;
+    
+    use strict;
+    use warnings;
+    use base 'DBIx::Class::ResultSet';
+    
+    =head2 created_after
+    
+    A predefined search for recently added books
+    
+    =cut
+    
+    sub created_after {
+      my ($self, $datetime) = @_;
+      
+      my $date_str = $self->_source_handle->schema->storage
+                            ->datetime_parser->format_datetime($datetime);
+    
+      return $self->search({
+          created => { '>' => $date_str }
+      });
+    }
+    
+    1;
+
+Then we need to tell the Result Class to to treat this as a ResultSet 
+Class.  Open C<lib/MyApp/Schema/Result/Books.pm> and add the following 
+above the "C<1;>" at the bottom of the file:
+
+    #
+    # Set ResultSet Class
+    #
+    __PACKAGE__->resultset_class('MyApp::Schema::ResultSet::Books');
+
+Then add the following method to the C<lib/MyApp/Controller/Books.pm>:
+
+    =head2 list_recent
+    
+    List recently created books
+    
+    =cut
+    
+    sub list_recent :Chained('base') :PathPart('list_recent') :Args(1) {
+        my ($self, $c, $mins) = @_;
+    
+        # Retrieve all of the book records as book model objects and store in the
+        # stash where they can be accessed by the TT template, but only
+        # retrieve books created within the last $min number of minutes
+        $c->stash->{books} = [$c->model('DB::Books')
+                                ->created_after(DateTime->now->subtract(minutes => $mins))];
+    
+        # Set the TT template to use.  You will almost always want to do this
+        # in your action methods (action methods respond to user input in
+        # your controllers).
+        $c->stash->{template} = 'books/list.tt2';
+    }
+
+Now start the development server with C<DBIC_TRACE=1> and try 
+different values for the minutes argument (the final number value) for 
+the URL C<http://localhost:3000/books/list_recent/10>.  For example, 
+this would list all books added in the last fifteen minutes:
+
+    http://localhost:3000/books/list_recent/15
+
+Depending on how recently you added books, you might want to
+try a higher or lower value.
+
+
+=head2 Chaining ResultSets
+
+One of the most helpful and powerful features in DBIC is that it 
+allows you to "chain together" a series of queries (note that this has 
+nothing to do with the "Chained Dispatch" for Catalyst that we were 
+discussing above).  Because each ResultSet returns another ResultSet, 
+you can take an initial query and immediately feed that into a second 
+query (and so on for as many queries you need).  And, because this 
+technique carries over to the ResultSet Class feature we implemented 
+in the previous section for our "canned search", we can combine the 
+two capabilities.  For example, let's add an action to our C<Books> 
+controller that lists books that are both recent I<and> have "TCP" in 
+the title.  Open up C<lib/MyApp/Controller/Books.pm> and add the 
+following method:
+
+    =head2 list_recent
+    
+    List recently created books
+    
+    =cut
+    
+    sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
+        my ($self, $c, $mins) = @_;
+    
+        # Retrieve all of the book records as book model objects and store in the
+        # stash where they can be accessed by the TT template, but only
+        # retrieve books created within the last $min number of minutes
+        # AND that have 'TCP' in the title
+        $c->stash->{books} = [$c->model('DB::Books')
+                                ->created_after(DateTime->now->subtract(minutes => $mins))
+                                ->search({title => {'like', '%TCP%'}})
+                             ];
+    
+        # Set the TT template to use.  You will almost always want to do this
+        # in your action methods (action methods respond to user input in
+        # your controllers).
+        $c->stash->{template} = 'books/list.tt2';
+    }
+
+To try this out, restart the development server with:
+
+    DBIC_TRACE=1 script/myapp_server.pl
+
+And enter the following URL into your browser:
+
+    http://localhost:3000/books/list_recent_tcp/100
+
+And you should get a list of books added in the last 100 minutes that 
+contain the string "TCP" in the title.  However, if you look at all 
+books within the last 100 minutes, you should get a longer list 
+(again, you might have to adjust the number of minutes depending on 
+how recently you added books to your database):
+
+    http://localhost:3000/books/list_recent/100
+
+Take a look at the DBIC_TRACE output in the development server log for 
+the first URL and you should see something similar to the following:
+
+    SELECT me.id, me.title, me.rating, me.created, me.updated FROM books me 
+    WHERE ( ( ( title LIKE ? ) AND ( created > ? ) ) ): '%TCP%', '2009-03-05 15:52:57'
+
+However, let's not pollute our controller code with this raw "TCP" 
+query -- it would be cleaner to encapsulate that code in a method on 
+our ResultSet Class.  To do this, open 
+C<lib/MyApp/Schema/ResultSet/Books.pm> and add the following method:
+
+    =head2 title_like
+    
+    A predefined search for books with a 'LIKE' search in the string
+    
+    =cut
+    
+    sub title_like {
+      my ($self, $title_str) = @_;
+      
+      return $self->search({
+          title => { 'like' => "%$title_str%" }
+      });
+    }
+
+We defined the search string as C<$title_str> to make the method more 
+flexible.  Now update the C<list_recent_tcp> method in 
+C<lib/MyApp/Controller/Books.pm> to match the following (we have 
+replaced the C<-E<gt>search> line with the C<-E<gt>title_like> line 
+shown here -- the rest of the method should be the same):
+
+    =head2 list_recent_tcp
+    
+    List recently created books
+    
+    =cut
+    
+    sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
+        my ($self, $c, $mins) = @_;
+    
+        # Retrieve all of the book records as book model objects and store in the
+        # stash where they can be accessed by the TT template, but only
+        # retrieve books created within the last $min number of minutes
+        # AND that have 'TCP' in the title
+        $c->stash->{books} = [$c->model('DB::Books')
+                                ->created_after(DateTime->now->subtract(minutes => $mins))
+                                ->title_like('TCP')
+                             ];
+    
+        # Set the TT template to use.  You will almost always want to do this
+        # in your action methods (action methods respond to user input in
+        # your controllers).
+        $c->stash->{template} = 'books/list.tt2';
+    }
+
+Then restart the development server and try out the C<list_recent_tcp> 
+and C<list_recent> URL as we did above.  It should work just the same, 
+but our code is obviously cleaner and more modular, while also being 
+more flexible at the same time.
+
+
+=head2 Adding Methods to Result Classes
+
+In the previous two sections we saw a good example of how we could use 
+DBIC ResultSet Classes to clean up our code for an entire query (for 
+example, our "canned searches" that filtered the entire query).  We 
+can do a similar improvement when working with individual rows as 
+well.  Whereas the ResultSet construct is used in DBIC to correspond 
+to an entire query, the Result Class construct is used to represent a 
+row. Therefore, we can add row-specific "helper methods" to our Result 
+Classes stored in C<lib/MyApp/Schema/Result/>. For example, open 
+C<lib/MyApp/Schema/Result/Authors.pm> and add the following method 
+(as always, it must be above the closing "C<1;>"):
+
+    #
+    # Helper methods
+    #
+    sub full_name {
+        my ($self) = @_;
+    
+        return $self->first_name . ' ' . $self->last_name;
+    }
+
+This will allow us to conveniently retrieve both the first and last 
+name for an author in one shot.  Now open C<root/src/books/list.tt2> 
+and change the definition of C<tt_authors> from this:
+
+      [% tt_authors = [ ];
+         tt_authors.push(author.last_name) FOREACH author = book.authors %]
+
+to:
+
+      [% tt_authors = [ ];
+         tt_authors.push(author.full_name) FOREACH author = book.authors %]
+
+(Only C<author.last_name> was changed to C<author.full_name> -- the 
+rest of the file should remain the same.)
+
+Now restart the development server and go to the standard book list
+URL:
+
+    http://localhost:3000/books/list
+
+The "Author(s)" column will now contain both the first and last name. 
+And, because the concatenation logic was encapsulated inside our 
+Result Class, it keeps the code inside our .tt template nice and clean 
+(remember, we want the templates to be as close to pure HTML markup as 
+possible). Obviously, this capability becomes even more useful as you 
+use to to remove even more complicated row-specific logic from your 
+templates!
+
+
 =head1 AUTHOR
 
 Kennedy Clark, C<hkclark@gmail.com>
diff --git a/lib/Catalyst/Manual/Tutorial/MoreCatalystBasics.pod b/lib/Catalyst/Manual/Tutorial/MoreCatalystBasics.pod
index 1c2086a..b4e584f 100644
--- a/lib/Catalyst/Manual/Tutorial/MoreCatalystBasics.pod
+++ b/lib/Catalyst/Manual/Tutorial/MoreCatalystBasics.pod
@@ -1111,30 +1111,8 @@ L<Catalyst::Model::DBIC::Schema|Catalyst::Model::DBIC::Schema> in
 Ubuntu 8.10 uses the older DBIC C<load_classes> vs. the newer 
 C<load_namspaces> technique.  For new applications, please try to use 
 C<load_namespaces> since it more easily supports a very useful DBIC
-technique called "ResultSet Classes."  This tutorial expects to migrate to 
-C<load_namespaces> when the next release of Ubuntu comes out.
-
-If you wish to try C<load_namespaces> now, you can manually do the
-equivalent of the C<create=static> operation outside of the Catalyst
-helper:
-
-    perl -MDBIx::Class::Schema::Loader=make_schema_at,dump_to_dir:./lib -e \
-        'make_schema_at("MyApp::Schema", { debug => 1, use_namespaces => 1, \
-        components => ["InflateColumn::DateTime"] },["dbi:SQLite:myapp.db", "", "" ])'
-
-And then use the helper to only create the Catalyst model class:
-
-    script/myapp_create.pl model DB DBIC::Schema MyApp::Schema dbi:SQLite:myapp.db
-
-B<However>, it is important to note that C<load_namespaces> will look 
-for your C<Books.pm>, <Authors.pm>, etc. files in 
-C<lib/MyApp/Schema/Result> (it adds the subdirection "Result" so that 
-there can also be a "ResultSet" directory next to it in the 
-hierarchy).  Therefore, if you switch to C<load_namespaces>, you will 
-need to modify the path to these "result class" files throughout the 
-rest of the tutorial.  Our recommendation for now would be to complete 
-the tutorial using C<load_classes> and the try converting to 
-C<load_namespaces> after you are done.
+technique called "ResultSet Classes."  We will migrate to 
+C<load_namespaces> in Part 4 (BasicCRUD) of this tutorial.
 
 
 =head2 Updating the Generated DBIC Schema Files