- =head1 NAME
+=head1 NAME
Catalyst::Manual::Tutorial::BasicCRUD - Catalyst Tutorial - Part 4: Basic CRUD
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 if you have DBIC_TRACE set:
+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'
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 |
- '-------------------------------------+--------------------------------------'
+ [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 |
- '-------------------------------------+--------------------------------------'
+ [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.
+section. And, the "/*/*/*" portion clearly shows our requirement for
+three arguments.
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
+ 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
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
- $c->log->debug('*** INSIDE BASE METHOD ***');
- }
-
-Here we print a log message and store the resultset in
+ =head2 base
+
+ Can place common logic to start chained dispatch here
+
+ =cut
+
+ sub base :Chained('/') :PathPart('books') :CaptureArgs(0) {
+ my ($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
+ $c->log->debug('*** INSIDE BASE METHOD ***');
+ }
+
+Here we print a log message and store the DBIC resultset in
C<$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
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
+book object with C<-E<gt>find($id)> 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
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 |
- '-------------------------------------+--------------------------------------'
+Next, try out the refactored chain by restarting the development
+server. 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
+ 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.
+rating of 5" message 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
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 |
- '-------------------------------------+--------------------------------------'
+ [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
=item *
If you are referring to a method in a different controller, you need
-to include that as an argument to C<controller()>, as in
+to include that controller's name as an argument to C<controller()>, as in
C<$c-E<gt>controller('_controller_name_')-E<gt>action_for('_method_name_')>.
=back
-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).
+B<Note:> In practice you should B<never> 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<base>
+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.
+because that logic does not belong in C<base> 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<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:
=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),
another_thing => 1});
-Either format works, but the C<$c-E<gt>stash(name => value);>
+Either format works, but the C<$c-E<gt>stash(name =E<gt> value);>
style is growing in popularity -- you may which to use it all
the time (even when you are only setting a single value).
=cut
sub delete :Chained('object') :PathPart('delete') :Args(0) {
- # $id = primary key of book to delete
my ($self, $c) = @_;
# Use the book object saved by 'object' and delete it along
This method first deletes the book object saved by the C<object> method.
However, it also removes the corresponding entry from the
-C<book_authors> table. Note that C<delete> will cascade to also delete
-the related join table entries in C<book_authors>.
+C<book_authors> table with a cascading delete.
Then, rather than forwarding to a "delete done" page as we did with the
earlier create example, it simply sets the C<status_msg> to display a
The C<delete> method now appears in the "Loaded Chained actions" section
of the startup debug output:
- [debug] Loaded Chained actions:
+ [debug] Loaded Chained actions:
.-------------------------------------+--------------------------------------.
| Path Spec | Private |
+-------------------------------------+--------------------------------------+
http://localhost:3000/books/delete/6
-What if the user were to press reload with this URL still active? In
-this case the redundant delete is harmless, but in other cases this
-could clearly be extremely dangerous.
+What if the user were to press reload with this URL still active? In
+this case the redundant delete is harmless (although it does generate
+an exception screen, it doesn't perform any undesirable actions on the
+application or database), but in other cases this could clearly be
+extremely dangerous.
We can improve the logic by converting to a redirect. Unlike
C<$c-E<gt>forward('list'))> or C<$c-E<gt>detach('list'))> that perform
=cut
sub delete :Chained('object') :PathPart('delete') :Args(0) {
- # $id = primary key of book to delete
- my ($self, $c, $id) = @_;
+ my ($self, $c) = @_;
# Use the book object saved by 'object' and delete it along
# with related 'book_authors' entries
# 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'));
+ $c->response->redirect($c->uri_for($self->action_for('list')));
}
=cut
sub delete :Chained('object') :PathPart('delete') :Args(0) {
- # $id = primary key of book to delete
- my ($self, $c, $id) = @_;
+ my ($self, $c) = @_;
# Use the book object saved by 'object' and delete it along
# with related 'book_authors' entries
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