=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<Part 3 of 9> for the Catalyst tutorial.
+This is B<Part 4 of 10> for the Catalyst tutorial.
L<Tutorial Overview|Catalyst::Manual::Tutorial>
=item 3
-B<Basic CRUD>
+L<More Catalyst Basics|Catalyst::Manual::Tutorial::MoreCatalystBasics>
=item 4
-L<Authentication|Catalyst::Manual::Tutorial::Authentication>
+B<Basic CRUD>
=item 5
-L<Authorization|Catalyst::Manual::Tutorial::Authorization>
+L<Authentication|Catalyst::Manual::Tutorial::Authentication>
=item 6
-L<Debugging|Catalyst::Manual::Tutorial::Debugging>
+L<Authorization|Catalyst::Manual::Tutorial::Authorization>
=item 7
-L<Testing|Catalyst::Manual::Tutorial::Testing>
+L<Debugging|Catalyst::Manual::Tutorial::Debugging>
=item 8
-L<AdvancedCRUD|Catalyst::Manual::Tutorial::AdvancedCRUD>
+L<Testing|Catalyst::Manual::Tutorial::Testing>
=item 9
+L<Advanced CRUD|Catalyst::Manual::Tutorial::AdvancedCRUD>
+
+=item 10
+
L<Appendices|Catalyst::Manual::Tutorial::Appendices>
=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<Book> 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<CatalystX::ListFramework::Builder|CatalystX::ListFramework::Builder>,
+L<CatalystX::CRUD|CatalystX::CRUD>, and
+L<CatalystX::CRUD::YUI|CatalystX::CRUD::YUI>.
You can checkout the source code for this example from the catalyst
subversion repository as per the instructions in
-L<Catalyst::Manual::Tutorial::Intro>
+L<Catalyst::Manual::Tutorial::Intro|Catalyst::Manual::Tutorial::Intro>.
+
=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
# 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
});
[% # Provide a link back to the list page -%]
[% # 'uri_for()' builds a full URI; e.g., 'http://localhost:3000/books/list' -%]
- <p><a href="[% Catalyst.uri_for('/books/list') %]">Return to list</a></p>
+ <p><a href="[% c.uri_for('/books/list') %]">Return to list</a></p>
[% # Try out the TT Dumper (for development only!) -%]
<pre>
[% Dumper.dump(book) %]
</pre>
-The TT C<USE> 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<Data::Dumper>
-"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<USE> 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<Data::Dumper|Data::Dumper> "pretty printing" of objects and
+variables. Other than that, the rest of the code should be familiar
+from the examples in Part 3.
-B<IMPORTANT NOTE> As mentioned earlier, the C<MyApp::View::TT.pm> view
-class created by TTSite redefines the name used to access the Catalyst
-context object in TT templates from the usual C<c> to C<Catalyst>.
=head2 Try the C<url_create> Feature
If the application is still running from before, use C<Ctrl-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</books/url_create> appears in the startup debug
output.
http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
-Your browser should display " Added book 'TCPIP_Illustrated_Vol-2' by
+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:
+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'
the existing record for Richard Stevens. The C<SELECT> statement results
from DBIC automatically fetching the book for the C<Dumper.dump(book)>.
-If you then click the "Return to list" link, you should find that there
-are now six books shown (if necessary, Shift-Reload your browser at the
-C</books/list> page).
+If you then click the "Return to list" link, you should find that
+there are now six books shown (if necessary, Shift+Reload or
+Ctrl+Reload your browser at the C</books/list> page).
-Then I<add 2 more copies of the same book> so that we have some extras for
-our delete logic that will be coming up soon. Enter the same URL above
-two more times (or refresh your browser twice if it still contains this
-URL):
- http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
+=head1 CONVERT TO A CHAINED ACTION
+
+Although the example above uses the same C<Local> action type for the
+method that we saw in the previous part of the tutorial, there is an
+alternate approach that allows us to be more specific while also
+paving the way for more advanced capabilities. Change the method
+declaration for C<url_create> in C<lib/MyApp/Controller/Books.pm> you
+entered above to match the following:
+
+ sub url_create :Chained('/') :PathPart('books/url_create') :Args(3) {
+
+This converts the method to take advantage of the Chained
+action/dispatch type. Chaining let's you have a single URL
+automatically dispatch to several controller methods, each of which
+can have precise control over the number of arguments that it will
+receive. A chain can essentially be thought of having three parts --
+a beginning, a middle and an end. The bullets below summarize the key
+points behind each of these parts of a chain:
+
+
+=over 4
+
+
+=item *
+
+Beginning
+
+=over 4
+
+=item *
+
+B<Use "C<:Chained('/')>" to start a chain>
+
+=item *
+
+Get arguments through C<CaptureArgs()>
+
+=item *
+
+Specify the path to match with C<PathPart()>
+
+=back
+
+
+=item *
+
+Middle
+
+=over 4
+
+=item *
+
+Link to previous part of the chain with C<:Chained('_name_')>
+
+=item *
+
+Get arguments through C<CaptureArgs()>
+
+=item *
+
+Specify the path to match with C<PathPart()>
+
+=back
-You should be able to click "Return to list" and now see 3 copies of
-"TCP_Illustrated_Vol-2".
+
+=item *
+
+End
+
+=over 4
+
+=item *
+
+Link to previous part of the chain with C<:Chained('_name_')>
+
+=item *
+
+B<Do NOT get arguments through "C<CaptureArgs()>," use "C<Args()>" instead to end a chain>
+
+=item *
+
+Specify the path to match with C<PathPart()>
+
+=back
+
+
+=back
+
+In our C<url_create> method above, we have combined all 3 parts into a
+single method: C<:Chained('/')> to start the chain,
+C<:PathPart('books/url_create')> to specify the base URL to match,
+along with C<:Args(3)> to capture exactly 3 arguments and also end the
+chain.
+
+As we will see shortly, a chain can consist of as many "links" as you
+wish, with each part capturing some arguments and doing some work
+along the way. We will continue to use the Chained action type in this
+part of the tutorial and explore slightly more advanced capabilities
+with the base method and delete feature below. But Chained dispatch
+is capable of far more. For additional information, see
+L<Catalyst::Manual::Intro/Action types>,
+L<Catalyst::DispatchType::Chained|Catalyst::DispatchType::Chained>,
+and the 2006 advent calendar entry on the subject:
+L<http://www.catalystframework.org/calendar/2006/10>.
+
+
+=head2 Try the Chained Action
+
+If you look back at the development server startup logs from your
+initial version of the C<url_create> method (the one using the
+C<:Local> attribute), you will notice that it produced output similar
+to the following:
+
+ [debug] Loaded Path actions:
+ .-------------------------------------+--------------------------------------.
+ | Path | Private |
+ +-------------------------------------+--------------------------------------+
+ | / | /default |
+ | / | /index |
+ | /books | /books/index |
+ | /books/list | /books/list |
+ | /books/url_create | /books/url_create |
+ '-------------------------------------+--------------------------------------'
+
+Now start the development server with our basic chained method in
+place and the startup debug output should change to something along
+the lines of the following:
+
+ [debug] Loaded Path actions:
+ .-------------------------------------+--------------------------------------.
+ | Path | Private |
+ +-------------------------------------+--------------------------------------+
+ | / | /default |
+ | / | /index |
+ | /books | /books/index |
+ | /books/list | /books/list |
+ '-------------------------------------+--------------------------------------'
+
+ [debug] Loaded Chained actions:
+ .-------------------------------------+--------------------------------------.
+ | Path Spec | Private |
+ +-------------------------------------+--------------------------------------+
+ | /books/url_create/*/*/* | /books/url_create |
+ '-------------------------------------+--------------------------------------'
+
+C<url_create> has disappeared form the "Loaded Path actions" section
+but it now shows up under the newly created "Loaded Chained actions"
+section. And, the "/*/*/*" portion clearly shows that we have
+specified that 3 arguments are required.
+
+As with our non-chained version of C<url_create>, use your browser to
+enter the following URL:
+
+ http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
+
+You should see the same "Added book 'TCPIP_Illustrated_Vol-2' by
+'Stevens' with a rating of 5." along with a dump of the new book model
+object. Click the "Return to list" link, you should find that there
+are now seven books shown (two copies of TCPIP_Illustrated_Vol-2).
+
+
+=head2 Refactor to Use a "Base" Method to Start the Chains
+
+Let's make a quick update to our initial Chained action to show a
+little more of the power of chaining. First, open
+C<lib/MyApp/Controller/Books.pm> in your editor and add the following
+method:
+
+ =head2 base
+
+ Can place common logic to start chained dispatch here
+
+ =cut
+
+ sub base :Chained('/') :PathPart('books') :CaptureArgs(0) {
+ my ($self, $c) = @_;
+
+ # 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
+ $c->log->debug('*** INSIDE BASE METHOD ***');
+ }
+
+Here we print a log message and store the resultset in
+C<$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
+capture that argument (with C<:CaptureArgs(1)>) and use it to pull the
+book object with that ID from the database and leave it in the stash for
+later parts of your chains to then act upon. Because we have several
+actions that don't need to retrieve a book (such as the C<url_create>
+we are working with now), we will instead add that functionality
+to a common C<object> action shortly.
+
+As for C<url_create>, let's modify it to first dispatch to C<base>.
+Open up C<lib/MyApp/Controller/Books.pm> and edit the declaration for
+C<url_create> to match the following:
+
+ sub url_create :Chained('base') :PathPart('url_create') :Args(3) {
+
+Next, let's try out our refactored chain. Restart the development
+server and notice that our "Loaded Chained actions" section has
+changed slightly:
+
+ [debug] Loaded Chained actions:
+ .-------------------------------------+--------------------------------------.
+ | Path Spec | Private |
+ +-------------------------------------+--------------------------------------+
+ | /books/url_create/*/*/* | /books/base (0) |
+ | | => /books/url_create |
+ '-------------------------------------+--------------------------------------'
+
+The "Path Spec" is the same, but now it maps to two Private actions as
+we would expect.
+
+Once again, enter the following URL into your browser:
+
+ http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
+
+The same "Added book 'TCPIP_Illustrated_Vol-2' by 'Stevens' with a
+rating of 5." and dump of the new book object should appear. Also
+notice the extra debug message in the development server output from
+the C<base> method. Click the "Return to list" link, you should find
+that there are now eight books shown.
=head1 MANUALLY BUILDING A CREATE FORM
=cut
- sub form_create : Local {
+ sub form_create :Chained('base') :PathPart('form_create') :Args(0) {
my ($self, $c) = @_;
# Set the TT template to use
This action simply invokes a view containing a book creation form.
+
=head2 Add a Template for the Form
Open C<root/src/books/form_create.tt2> in your editor and enter:
[% META title = 'Manual Form Book Create' -%]
- <form method="post" action="[% Catalyst.uri_for('form_create_do') %]">
+ <form method="post" action="[% c.uri_for('form_create_do') %]">
<table>
<tr><td>Title:</td><td><input type="text" name="title"></td></tr>
<tr><td>Rating:</td><td><input type="text" name="rating"></td></tr>
Note that we have specified the target of the form data as
C<form_create_do>, the method created in the section that follows.
+
=head2 Add a Method to Process Form Values and Update Database
Edit C<lib/MyApp/Controller/Books.pm> and add the following method to
=cut
- sub form_create_do : Local {
+ sub form_create_do :Chained('base') :PathPart('form_create_do') :Args(0) {
my ($self, $c) = @_;
# Retrieve the values from the form
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,
});
$ 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<http://localhost:3000/books/form_create> 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<create_done.tt2> template seen in earlier examples. Finally, click
"Return to list" to view the full list of books.
B<Note:> 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
</td>
<td>
[% # Add a link to delete a book %]
- <a href="[% Catalyst.uri_for('delete/') _ book.id %]">Delete</a>
+ <a href="[% c.uri_for('id', book.id, 'delete') %]">Delete</a>
</td>
</tr>
[% END -%]
</table>
-The additional code is obviously designed to add a new column to the
-right side of the table with a C<Delete> "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<Delete> "button" (for simplicity,
+links will be used instead of full HTML buttons).
+
+B<Note:> You should use more than just a simple link with your
+applications. Consider using some sort of of confirmation page
+(typically with unique actions in your controller for both the
+confirmation and the actual delete operation). Also, you should try
+to use an HTTP POST operation (versus the GET used here) for
+operations that change the state of your application (e.g., the
+database).
+
+
+=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<base>
+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<base> doesn't mean that we can't
+create another location to centralize that logic. In our case, we will
+create a method called C<object> 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<url_create> that don't
+operate on an existing book can chain directly off base.
+
+To add the C<object> method, edit C<lib/MyApp/Controller/Books.pm>
+and add the following code:
+
+ sub object :Chained('base') :PathPart('id') :CaptureArgs(1) {
+ 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<object> will automatically
+have the appropriate book waiting for it in
+C<$c-E<gt>stash-Egt>{object}>.
+
+Also note that we are using different technique for setting
+C<$c-E<gt>stash>. 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-E<gt>stash(name => 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<lib/MyApp/Controller/Books.pm> in your editor and add the
following method:
- =head2 delete
+ =head2 delete
Delete a book
=cut
- sub delete : Local {
+ sub delete :Chained('object') :PathPart('delete') :Args(0) {
# $id = primary key of book to delete
- my ($self, $c, $id) = @_;
+ my ($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.";
$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<book_authors> table. Note that C<delete_all> was used instead of
-C<delete>: whereas C<delete_all> also removes the join table entries in
-C<book_authors>, C<delete> does not (only use C<delete_all> if you
-really need the cascading deletes... otherwise you are wasting resources).
+This method first deletes the book object saved by the C<object> method.
+However, it also removes the corresponding entry from the
+C<book_authors> table. Note that C<delete> will cascade to also delete
+the related join table entries in C<book_authors>.
Then, rather than forwarding to a "delete done" page as we did with the
earlier create example, it simply sets the C<status_msg> to display a
If the application is still running from before, use C<Ctrl-C> to kill
it. Then restart the server:
- $ script/myapp_server.pl
+ $ DBIC_TRACE=1 script/myapp_server.pl
+
+The C<delete> 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<http://localhost:3000/books/list> 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
We can improve the logic by converting to a redirect. Unlike
C<$c-E<gt>forward('list'))> or C<$c-E<gt>detach('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.
open C<lib/MyApp/Controller/Books.pm> and edit the existing
C<sub delete> method to match:
- =head2 delete
+ =head2 delete
Delete a book
-
+
=cut
- sub delete : Local {
+ sub delete :Chained('object') :PathPart('delete') :Args(0) {
# $id = primary key of book to delete
my ($self, $c, $id) = @_;
- # 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.";
=head2 Try the Delete and Redirect Logic
Restart the development server and point your browser to
-L<http://localhost:3000/books/list>. Delete the first copy of
-"TCPIP_Illustrated_Vol-2", but notice that I<no green "Book deleted"
-status message is displayed>. Because the stash is reset on every
-request (and a redirect involves a second request), the
-C<status_msg> is cleared before it can be displayed.
+L<http://localhost:3000/books/list> (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<http://localhost:3000/books/list> URL, so that is an
+improvement, but notice that I<no green "Book deleted" status message is
+displayed>. Because the stash is reset on every request (and a redirect
+involves a second request), the C<status_msg> is cleared before it can
+be displayed.
=head2 Using C<uri_for> to Pass Query Parameters
-There are several ways to pass information across a redirect.
-In general, the best option is to use the C<flash> 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<lib/MyApp/Controller/Books.pm> and update the existing
-C<sub delete> method to match the following:
+There are several ways to pass information across a redirect. One
+option is to use the C<flash> 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<lib/MyApp/Controller/Books.pm> and update the existing C<sub delete>
+method to match the following:
=head2 delete
=cut
- sub delete : Local {
+ sub delete :Chained('object') :PathPart('delete') :Args(0) {
# $id = primary key of book to delete
my ($self, $c, $id) = @_;
- # 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',
This modification simply leverages the ability of C<uri_for> to include
an arbitrary number of name/value pairs in a hash reference. Next, we
-need to update C<root/lib/site/layout> to handle C<status_msg> as a
+need to update C<root/src/wrapper.tt2> to handle C<status_msg> as a
query parameter:
- <div id="header">[% PROCESS site/header %]</div>
-
+ ...
<div id="content">
- <span class="message">[% status_msg || Catalyst.request.params.status_msg %]</span>
- <span class="error">[% error_msg %]</span>
- [% content %]
- </div>
-
- <div id="footer">[% PROCESS site/footer %]</div>
+ [%# Status and error messages %]
+ <span class="message">[% status_msg || c.request.params.status_msg %]</span>
+ <span class="error">[% error_msg %]</span>
+ [%# This is where TT will stick all of your template's contents. -%]
+ [% content %]
+ </div><!-- end content -->
+ ...
+
+Although the sample above only shows the C<content> div, leave the
+rest of the file intact -- the only change we made to the C<wrapper.tt2>
+was to add "C<|| c.request.params.status_msg>" to the
+C<E<lt>span class="message"E<gt>> line.
=head2 Try the Delete and Redirect With Query Param Logic
Restart the development server and point your browser to
-L<http://localhost:3000/books/list>. Then delete the remaining copy
-of "TCPIP_Illustrated_Vol-2". The green "Book deleted" status message
+L<http://localhost:3000/books/list> (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<NOTE:> Although this did present an opportunity to show a handy
-capability of C<uri_for>, it would be much better to use Catalyst's
-C<flash> 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<flash>,
-this message returns to its rightful place as a service-side
-mechanism (we will migrate this code to C<flash> in the next part
-of the tutorial).
+B<NOTE:> Another popular method for maintaining server-side
+information across a redirect is to use the C<flash> technique we
+discuss in the next part of the tutorial,
+L<Authentication|Catalyst::Manual::Tutorial::Authentication>. While
+C<flash> is a "slicker" mechanism in that it's all handled by the
+server and doesn't "pollute" your URLs, B<it is important to note that
+C<flash> 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 AUTHOR
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-Manual/lib/Catalyst/Manual/Tutorial/>.
-
-Copyright 2006, Kennedy Clark, under Creative Commons License
-(L<http://creativecommons.org/licenses/by-nc-sa/2.5/>).
+L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/>.
+Copyright 2006-2008, Kennedy Clark, under Creative Commons License
+(L<http://creativecommons.org/licenses/by-sa/3.0/us/>).
projects / catagits/Catalyst-Manual.git / blobdiff