From a36e74fb1f7e67d038dd1c6c6e4a8ca642f225f9 Mon Sep 17 00:00:00 2001 From: Alex Beamish Date: Wed, 4 Sep 2013 13:45:39 -0400 Subject: [PATCH] Documentation update and cleanup This update removes 'year' from the CD table definition in both the SQL and in the class definition, since it wasn't being used. The directory MyApp/Schema/ResultSet was also removed since the supplied code never used it. The results that the sample code produces have been expanded a little so that they provide answers to the questions asked by the subroutine calls. A new section has been added that briefly discusses the results and explains the techniques that could be used when writing this type of a programmatic query. --- lib/DBIx/Class/Manual/Example.pod | 108 ++++++++++++++++++------------ 1 file changed, 66 insertions(+), 42 deletions(-) diff --git a/lib/DBIx/Class/Manual/Example.pod b/lib/DBIx/Class/Manual/Example.pod index 59b114e80..05db57bd0 100644 --- a/lib/DBIx/Class/Manual/Example.pod +++ b/lib/DBIx/Class/Manual/Example.pod @@ -11,7 +11,7 @@ as the database frontend. The database consists of the following: table 'artist' with columns: artistid, name - table 'cd' with columns: cdid, artist, title, year + table 'cd' with columns: cdid, artist, title table 'track' with columns: trackid, cd, title @@ -25,21 +25,22 @@ And these rules exists: =head2 Installation -Install DBIx::Class via CPAN should be sufficient. +You'll need to install DBIx::Class via CPAN, and you'll also need to +install sqlite3 (not sqlite) if it's not already intalled. =head3 Create the database/tables -First make and change the directory: +First, create the database directory, then get into that directory, as +we'll create the database there: mkdir app - cd app - mkdir db - cd db + mkdir app/db + cd app/db This example uses SQLite which is a dependency of DBIx::Class, so you shouldn't have to install extra software. -Save the following into a example.sql in the directory db +Save the following into a example.sql in the directory app/db CREATE TABLE artist ( artistid INTEGER PRIMARY KEY, @@ -68,14 +69,13 @@ Change directory back from db to the directory app: cd ../ -Now create some more directories: +Now we'll create some more directories for the classes: mkdir MyApp mkdir MyApp/Schema mkdir MyApp/Schema/Result - mkdir MyApp/Schema/ResultSet -Then, create the following DBIx::Class::Schema classes: +Create the following DBIx::Class::Schema classes: MyApp/Schema.pm: @@ -104,7 +104,7 @@ MyApp/Schema/Result/Cd.pm: use base qw/DBIx::Class::Core/; __PACKAGE__->load_components(qw/InflateColumn::DateTime/); __PACKAGE__->table('cd'); - __PACKAGE__->add_columns(qw/ cdid artist title year/); + __PACKAGE__->add_columns(qw/ cdid artist title /); __PACKAGE__->set_primary_key('cdid'); __PACKAGE__->belongs_to('artist' => 'MyApp::Schema::Result::Artist'); __PACKAGE__->has_many('tracks' => 'MyApp::Schema::Result::Track'); @@ -126,7 +126,10 @@ MyApp/Schema/Result/Track.pm: =head3 Write a script to insert some records -insertdb.pl +This script should be created in the app/ directory, since it access the +database in the app/db directory. + +insertdb.pl: #!/usr/bin/perl @@ -186,8 +189,14 @@ insertdb.pl @tracks, ]); +Once created, this script should be run once to fill the database with +the required data for the following test script. + =head3 Create and run the test scripts +Like the previous script, this script should also be create in the app/ +directory. + testdb.pl: #!/usr/bin/perl @@ -242,7 +251,8 @@ testdb.pl: } ); while (my $track = $rs->next) { - print $track->title . "\n"; + print $track->title . " (from the CD '" . $track->cd->title + . "')\n"; } print "\n"; } @@ -260,7 +270,7 @@ testdb.pl: } ); my $cd = $rs->first; - print $cd->title . "\n\n"; + print $cd->title . " has the track '$tracktitle'.\n\n"; } sub get_cds_by_artist { @@ -296,7 +306,7 @@ testdb.pl: } ); my $artist = $rs->first; - print $artist->name . "\n\n"; + print $artist->name . " recorded the track '$tracktitle'.\n\n"; } sub get_artist_by_cd { @@ -311,37 +321,51 @@ testdb.pl: } ); my $artist = $rs->first; - print $artist->name . "\n\n"; + print $artist->name . " recorded the CD '$cdtitle'.\n\n"; } -It should output: - - get_tracks_by_cd(Bad): - Dirty Diana - Smooth Criminal - Leave Me Alone - - get_tracks_by_artist(Michael Jackson): - Beat it - Billie Jean - Dirty Diana - Smooth Criminal - Leave Me Alone - - get_cd_by_track(Stan): - The Marshall Mathers LP - - get_cds_by_artist(Michael Jackson): - Thriller - Bad - - get_artist_by_track(Dirty Diana): - Michael Jackson - - get_artist_by_cd(The Marshall Mathers LP): - Eminem +When this script is run, it should output the following: + + get_tracks_by_cd(Bad): + Leave Me Alone + Smooth Criminal + Dirty Diana + + get_tracks_by_artist(Michael Jackson): + Billie Jean (from the CD 'Thriller') + Leave Me Alone (from the CD 'Bad') + Smooth Criminal (from the CD 'Bad') + Beat It (from the CD 'Thriller') + Dirty Diana (from the CD 'Bad') + + get_cd_by_track(Stan): + The Marshall Mathers LP has the track 'Stan'. + + get_cds_by_artist(Michael Jackson): + Thriller + Bad + + get_artist_by_track(Dirty Diana): + Michael Jackson recorded the track 'Dirty Diana'. + + get_artist_by_cd(The Marshall Mathers LP): + Eminem recorded the CD 'The Marshall Mathers LP'. + +=head3 Discussion about the results + +The data model defined in this example has an artist with multiple CDs, +and a CD with multiple tracks; thus, it's simple to traverse from a +track back to a CD, and from there back to an artist. This is +demonstrated in the get_tracks_by_artist routine, where we easily walk +from the individual track back to the title of the CD that the track +came from ($track->cd->title). + +Note also that in the get_tracks_by_cd and get_tracks_by_artist +routines, the result set is called multiple times with the 'next' +iterator. In contrast, get_cd_by_track uses the 'first' result set +method, since only one CD is expected to have a specific track. =head1 Notes