X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?p=catagits%2FCatalyst-Manual.git;a=blobdiff_plain;f=lib%2FCatalyst%2FManual%2FTutorial%2FBasicCRUD.pod;h=ac5261dfbdd4d00f118c9607312dcb369285c241;hp=25d419e7ad212f9ff13931ca7c7a63627e1ee830;hb=c16b23ababd7cc92688183b0c72480966a7876b4;hpb=5edc2aaeb0c2dd02f1418b8e20c8a610d3779e29 diff --git a/lib/Catalyst/Manual/Tutorial/BasicCRUD.pod b/lib/Catalyst/Manual/Tutorial/BasicCRUD.pod index 25d419e..ac5261d 100644 --- a/lib/Catalyst/Manual/Tutorial/BasicCRUD.pod +++ b/lib/Catalyst/Manual/Tutorial/BasicCRUD.pod @@ -1,11 +1,11 @@ =head1 NAME -Catalyst::Manual::Tutorial::BasicCRUD - Catalyst Tutorial - Part 3: Basic CRUD +Catalyst::Manual::Tutorial::BasicCRUD - Catalyst Tutorial - Part 4: Basic CRUD =head1 OVERVIEW -This is B for the Catalyst tutorial. +This is B for the Catalyst tutorial. L @@ -21,57 +21,69 @@ L =item 3 -B +L =item 4 -L +B =item 5 -L +L =item 6 -L +L =item 7 -L +L =item 8 -L +L =item 9 +L + +=item 10 + L =back - =head1 DESCRIPTION This part of the tutorial builds on the fairly primitive application -created in Part 2 to add basic support for Create, Read, Update, and +created in Part 3 to add basic support for Create, Read, Update, and Delete (CRUD) of C objects. Note that the 'list' function in Part 2 already implements the Read portion of CRUD (although Read normally refers to reading a single object; you could implement full read functionality using the techniques introduced below). This section will focus on the Create and Delete aspects of CRUD. More advanced capabilities, including full Update functionality, will be addressed in -Part 8. +Part 9. + +Although this part of the tutorial will show you how to build CRUD +functionality yourself, another option is to use a "CRUD builder" type +of tool to automate the process. You get less control, but it's quick +and easy. For example, see +L, +L, and +L. You can checkout the source code for this example from the catalyst subversion repository as per the instructions in -L +L. + =head1 FORMLESS SUBMISSION -Our initial attempt at object creation will utilize the "URL arguments" -feature of Catalyst (we will employ the more common form-based -submission in the sections that follow). +Our initial attempt at object creation will utilize the "URL +arguments" feature of Catalyst (we will employ the more common form- +based submission in the sections that follow). =head2 Include a Create Action in the Books Controller @@ -93,7 +105,7 @@ Edit C and enter the following method: # Call create() on the book model object. Pass the table # columns/field values we want to set as hash values - my $book = $c->model('MyAppDB::Book')->create({ + my $book = $c->model('DB::Books')->create({ title => $title, rating => $rating }); @@ -160,7 +172,7 @@ Edit C and then enter: [% # Provide a link back to the list page -%] [% # 'uri_for()' builds a full URI; e.g., 'http://localhost:3000/books/list' -%] -

Return to list

+

Return to list

[% # Try out the TT Dumper (for development only!) -%] 
@@ -168,22 +180,20 @@ Edit C and then enter:
     [% Dumper.dump(book) %]
-The TT C directive allows access to a variety of plugin modules (TT -plugins, that is, not Catalyst plugins) to add extra functionality to -the base TT capabilities. Here, the plugin allows L -"pretty printing" of objects and variables. Other than that, the rest -of the code should be familiar from the examples in Part 2. +The TT C directive allows access to a variety of plugin modules +(TT plugins, that is, not Catalyst plugins) to add extra functionality +to the base TT capabilities. Here, the plugin allows +L "pretty printing" of objects and +variables. Other than that, the rest of the code should be familiar +from the examples in Part 3. -B As mentioned earlier, the C view -class created by TTSite redefines the name used to access the Catalyst -context object in TT templates from the usual C to C. =head2 Try the C Feature If the application is still running from before, use C to kill it. Then restart the server: - $ script/myapp_server.pl + $ DBIC_TRACE=1 script/myapp_server.pl Note that new path for C appears in the startup debug output. @@ -199,10 +209,11 @@ Next, use your browser to enter the following URL: http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4 -Your browser should display " Added book 'TCPIP_Illustrated_Vol-2' by -'Stevens' with a rating of 5." along with a dump of the new book model -object. You should also see the following DBIC debug messages displayed -in the development server log messages: +Your browser should display "Added book 'TCPIP_Illustrated_Vol-2' by +'Stevens' with a rating of 5." along with a dump of the new book model +object as it was returned by DBIC. You should also see the following +DBIC debug messages displayed in the development server log messages +if you have DBIC_TRACE set: INSERT INTO books (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2' INSERT INTO book_authors (author_id, book_id) VALUES (?, ?): `4', `6' @@ -214,19 +225,236 @@ The C statements are obviously adding the book and linking it to the existing record for Richard Stevens. The C Rating: @@ -274,6 +503,7 @@ Open C in your editor and enter: Note that we have specified the target of the form data as C, the method created in the section that follows. + =head2 Add a Method to Process Form Values and Update Database Edit C and add the following method to @@ -285,7 +515,7 @@ save the form information to the database: =cut - sub form_create_do : Local { + sub form_create_do :Chained('base') :PathPart('form_create_do') :Args(0) { my ($self, $c) = @_; # Retrieve the values from the form @@ -294,7 +524,7 @@ save the form information to the database: my $author_id = $c->request->params->{author_id} || '1'; # Create the book - my $book = $c->model('MyAppDB::Book')->create({ + my $book = $c->model('DB::Books')->create({ title => $title, rating => $rating, }); @@ -320,15 +550,30 @@ it. Then restart the server: $ script/myapp_server.pl +Notice that the server startup log reflects the two new chained +methods that we added: + + [debug] Loaded Chained actions: + .-------------------------------------+--------------------------------------. + | Path Spec | Private | + +-------------------------------------+--------------------------------------+ + | /books/form_create | /books/base (0) | + | | => /books/form_create | + | /books/form_create_do | /books/base (0) | + | | => /books/form_create_do | + | /books/url_create/*/*/* | /books/base (0) | + | | => /books/url_create | + '-------------------------------------+--------------------------------------' + Point your browser to L and enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an -author ID of 4. You should then be forwarded to the same +author ID of 4. You should then see the output of the same C template seen in earlier examples. Finally, click "Return to list" to view the full list of books. B Having the user enter the primary key ID for the author is obviously crude; we will address this concern with a drop-down list in -Part 8. +Part 9. =head1 A SIMPLE DELETE FEATURE @@ -340,7 +585,7 @@ from the database. =head2 Include a Delete Link in the List -Edit C and update it to the following (two +Edit C and update it to match the following (two sections have changed: 1) the additional 'Links' table header, and 2) the four lines for the Delete link near the bottom). @@ -376,33 +621,123 @@ and 2) the four lines for the Delete link near the bottom). [% # Add a link to delete a book %] - Delete + Delete [% END -%] -The additional code is obviously designed to add a new column to the -right side of the table with a C "button" (for simplicity, links -will be used instead of full HTML buttons). +The additional code is obviously designed to add a new column to the +right side of the table with a C "button" (for simplicity, +links will be used instead of full HTML buttons). + +Also notice that we are using a more advanced form of C than +we have seen before. Here we use C<$c-Econtroller- +Eaction_for> to automatically generate a URI appropriate for that +action based on the method we want to link to while inserting the +C value into the appropriate place. Now, if you ever change +C<:PathPart('delete')> in your controller method to +C<:PathPart('kill')>, then your links will automatically update +without any changes to your .tt2 template file. As long as the name +of your method does not changed ("delete" here), then your links will +still be correct. There are a few shortcuts and options when using +C: + +=over 4 + +=item * + +If you are referring to a method in the current controller, you can +use C<$self-Eaction_for('_method_name_')>. + +=item * + +If you are referring to a method in a different controller, you need +to include that controller's name as an argument to C, as in +C<$c-Econtroller('_controller_name_')-Eaction_for('_method_name_')>. + +=back + +B In practice you should B use a GET request to delete a +record -- always use POST for actions that will modify data. We are +doing it here for illustrative and simplicity purposes only. + + +=head2 Add a Common Method to Retrieve a Book for the Chain + +As mentioned earlier, since we have a mixture of actions that operate +on a single book ID and others that do no, we should not have C +capture the book ID, find the corresponding book in the database and +save it in the stash for later links in the chain. However, just +because that logic does not belong in C doesn't mean that we +can't create another location to centralize the book lookup code. In +our case, we will create a method called C that will store the +specific book in the stash. Chains that always operate on a single +existing book can chain off this method, but methods such as +C that don't operate on an existing book can chain +directly off base. + +To add the C method, edit C +and add the following code: + + =head2 object + + Fetch the specified book object based on the book ID and store + it in the stash + + =cut + + sub object :Chained('base') :PathPart('id') :CaptureArgs(1) { + # $id = primary key of book to delete + my ($self, $c, $id) = @_; + + # Find the book object and store it in the stash + $c->stash(object => $c->stash->{resultset}->find($id)); + + # Make sure the lookup was successful. You would probably + # want to do something like this in a real app: + # $c->detach('/error_404') if !$c->stash->{object}; + die "Book $id not found!" if !$c->stash->{object}; + } + +Now, any other method that chains off C will automatically +have the appropriate book waiting for it in +C<$c-Estash-Egt>{object}>. + +Also note that we are using different technique for setting +C<$c-Estash>. The advantage of this style is that it let's you +set multiple stash variables at a time. For example: + + $c->stash(object => $c->stash->{resultset}->find($id), + another_thing => 1); + +or as a hashref: + + $c->stash({object => $c->stash->{resultset}->find($id), + another_thing => 1}); + +Either format works, but the C<$c-Estash(name =E value);> +style is growing in popularity -- you may which to use it all +the time (even when you are only setting a single value). + =head2 Add a Delete Action to the Controller Open C in your editor and add the following method: - =head2 delete + =head2 delete Delete a book =cut - sub delete : Local { - # $id = primary key of book to delete - my ($self, $c, $id) = @_; + sub delete :Chained('object') :PathPart('delete') :Args(0) { + my ($self, $c) = @_; - # Search for the book and then delete it - $c->model('MyAppDB::Book')->search({id => $id})->delete_all; + # Use the book object saved by 'object' and delete it along + # with related 'book_authors' entries + $c->stash->{object}->delete; # Set a status message to be displayed at the top of the view $c->stash->{status_msg} = "Book deleted."; @@ -411,12 +746,9 @@ following method: $c->forward('list'); } -This method first deletes the book with the specified primary key ID. -However, it also removes the corresponding entry from the -C table. Note that C was used instead of -C: whereas C also removes the join table entries in -C, C does not (only use C if you -really need the cascading deletes... otherwise you are wasting resources). +This method first deletes the book object saved by the C method. +However, it also removes the corresponding entry from the +C table with a cascading delete. Then, rather than forwarding to a "delete done" page as we did with the earlier create example, it simply sets the C to display a @@ -434,12 +766,35 @@ equivalent. If the application is still running from before, use C to kill it. Then restart the server: - $ script/myapp_server.pl + $ DBIC_TRACE=1 script/myapp_server.pl + +The C method now appears in the "Loaded Chained actions" section +of the startup debug output: + + [debug] Loaded Chained actions: + .-------------------------------------+--------------------------------------. + | Path Spec | Private | + +-------------------------------------+--------------------------------------+ + | /books/id/*/delete | /books/base (0) | + | | -> /books/object (1) | + | | => /books/delete | + | /books/form_create | /books/base (0) | + | | => /books/form_create | + | /books/form_create_do | /books/base (0) | + | | => /books/form_create_do | + | /books/url_create/*/*/* | /books/base (0) | + | | => /books/url_create | + '-------------------------------------+--------------------------------------' Then point your browser to L and click the "Delete" link next to the first "TCPIP_Illustrated_Vol-2". A green "Book deleted" status message should display at the top of the page, -along with a list of the eight remaining books. +along with a list of the eight remaining books. You will also see the +cascading delete operation via the DBIC_TRACE output: + + DELETE FROM books WHERE ( id = ? ): '6' + SELECT me.book_id, me.author_id FROM book_authors me WHERE ( me.book_id = ? ): '6' + DELETE FROM book_authors WHERE ( author_id = ? AND book_id = ? ): '4', '6' =head2 Fixing a Dangerous URL @@ -449,14 +804,16 @@ prior step -- it is still referencing the delete action: http://localhost:3000/books/delete/6 -What if the user were to press reload with this URL still active? In -this case the redundant delete is harmless, but in other cases this -could clearly be extremely dangerous. +What if the user were to press reload with this URL still active? In +this case the redundant delete is harmless (although it does generate +an exception screen, it doesn't perform any undesirable actions on the +application or database), but in other cases this could clearly be +extremely dangerous. We can improve the logic by converting to a redirect. Unlike C<$c-Eforward('list'))> or C<$c-Edetach('list'))> that perform a server-side alteration in the flow of processing, a redirect is a -client-side mechanism that causes the brower to issue an entirely +client-side mechanism that causes the browser to issue an entirely new request. As a result, the URL in the browser is updated to match the destination of the redirection URL. @@ -464,45 +821,50 @@ To convert the forward used in the previous section to a redirect, open C and edit the existing C method to match: - =head2 delete + =head2 delete Delete a book - + =cut - sub delete : Local { - # $id = primary key of book to delete - my ($self, $c, $id) = @_; + sub delete :Chained('object') :PathPart('delete') :Args(0) { + my ($self, $c) = @_; - # Search for the book and then delete it - $c->model('MyAppDB::Book')->search({id => $id})->delete_all; + # Use the book object saved by 'object' and delete it along + # with related 'book_authors' entries + $c->stash->{object}->delete; # Set a status message to be displayed at the top of the view $c->stash->{status_msg} = "Book deleted."; - # Redirect the user back to the list page - $c->response->redirect($c->uri_for('/books/list')); + # Redirect the user back to the list page. Note the use + # of $self->action_for as earlier in this section (BasicCRUD) + $c->response->redirect($c->uri_for($self->action_for('list'))); } =head2 Try the Delete and Redirect Logic Restart the development server and point your browser to -L. Delete the first copy of -"TCPIP_Illustrated_Vol-2", but notice that I. Because the stash is reset on every -request (and a redirect involves a second request), the -C is cleared before it can be displayed. +L (don't just hit "Refresh" in your +browser since we left the URL in an invalid state in the previous +section!) and delete the first copy of the remaining two +"TCPIP_Illustrated_Vol-2" books. The URL in your browser should return +to the L URL, so that is an +improvement, but notice that I. Because the stash is reset on every request (and a redirect +involves a second request), the C is cleared before it can +be displayed. =head2 Using C to Pass Query Parameters -There are several ways to pass information across a redirect. -In general, the best option is to use the C technique that we -will see in Part 4 of the tutorial; however, here we will pass the -information via query parameters on the redirect itself. Open -C and update the existing -C method to match the following: +There are several ways to pass information across a redirect. One +option is to use the C technique that we will see in Part 5 of +the tutorial; however, here we will pass the information via query +parameters on the redirect itself. Open +C and update the existing C +method to match the following: =head2 delete @@ -510,49 +872,515 @@ C method to match the following: =cut - sub delete : Local { - # $id = primary key of book to delete - my ($self, $c, $id) = @_; + sub delete :Chained('object') :PathPart('delete') :Args(0) { + my ($self, $c) = @_; - # Search for the book and then delete it - $c->model('MyAppDB::Book')->search({id => $id})->delete_all; + # Use the book object saved by 'object' and delete it along + # with related 'book_authors' entries + $c->stash->{object}->delete; # Redirect the user back to the list page with status msg as an arg - $c->response->redirect($c->uri_for('/books/list', + $c->response->redirect($c->uri_for($self->action_for('list'), {status_msg => "Book deleted."})); } This modification simply leverages the ability of C to include an arbitrary number of name/value pairs in a hash reference. Next, we -need to update C to handle C as a +need to update C to handle C as a query parameter: - - + ...
- [% status_msg || Catalyst.request.params.status_msg %] - [% error_msg %] - [% content %] -
- - + [%# Status and error messages %] + [% status_msg || c.request.params.status_msg %] + [% error_msg %] + [%# This is where TT will stick all of your template's contents. -%] + [% content %] + + ... + +Although the sample above only shows the C div, leave the +rest of the file intact -- the only change we made to the C +was to add "C<|| c.request.params.status_msg>" to the +Cspan class="message"E> line. =head2 Try the Delete and Redirect With Query Param Logic Restart the development server and point your browser to -L. Then delete the remaining copy -of "TCPIP_Illustrated_Vol-2". The green "Book deleted" status message +L (you should now be able to safely +hit "refresh" in your browser). Then delete the remaining copy of +"TCPIP_Illustrated_Vol-2". The green "Book deleted" status message should return. -B Although this did present an opportunity to show a handy -capability of C, it would be much better to use Catalyst's -C feature in this situation. Although the technique here is -less dangerous than leaving the delete URL in the client's browser, -we have still exposed the status message to the user. With C, -this message returns to its rightful place as a service-side -mechanism (we will migrate this code to C in the next part -of the tutorial). +B Another popular method for maintaining server-side +information across a redirect is to use the C technique we +discuss in the next part of the tutorial, +L. While +C is a "slicker" mechanism in that it's all handled by the +server and doesn't "pollute" your URLs, B can lead to situations where the wrong information shows up +in the wrong browser window if the user has multiple windows or +browser tabs open.> For example, Window A causes something to be +placed in the stash, but before that window performs a redirect, +Window B makes a request to the server and gets the status information +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 you will recall that we load our DBIC Result Classes +(Books.pm, Authors.pm and BookAuthors.pm) with in +C with the C feature. Although +this method is perfectly valid, the DBIC community has migrated to a +newer C 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. + +If you are following along in Ubuntu 8.10, you will need to +upgrade your version of +L +to 0.23 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"' + 0.23 + +Make sure you get version 0.22 or higher. + +B Ubuntu 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 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 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 feature, DBIC automatically looks for +your Result Class files in a subdirectory of the Schema directory +called C (the files in C were already there +from Part 3 of the tutorial; the files in C +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 (or from +L) +to the corresponding files in C. If you take +this approach, be sure to add C<::Result> to the end of +C in all three files (for example, in C, the +"peer class" in the C relationship needs to be changed from +C to C). + +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