X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FCatalyst%2FManual%2FTutorial%2FBasicCRUD.pod;h=6a8278f275d77a3f9440f90f2bdfde295ae639d2;hb=c5d94181a3ea5ce8c06b9c33c11954d8514eb120;hp=f2565f2bc4c15a4116bcb353ce9e115fef21b404;hpb=89d3dae9792c2edcea631295e9abc467db845b7c;p=catagits%2FCatalyst-Manual.git diff --git a/lib/Catalyst/Manual/Tutorial/BasicCRUD.pod b/lib/Catalyst/Manual/Tutorial/BasicCRUD.pod index f2565f2..6a8278f 100644 --- a/lib/Catalyst/Manual/Tutorial/BasicCRUD.pod +++ b/lib/Catalyst/Manual/Tutorial/BasicCRUD.pod @@ -209,10 +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 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' @@ -342,47 +343,47 @@ initial version of the C 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 | - '-------------------------------------+--------------------------------------' + [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 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, 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 @@ -390,62 +391,70 @@ 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 +=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 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) = @_; - - $c->log->debug('*** INSIDE BASE METHOD ***'); - } - -Although we only use the C method to create a log message, we -could obviously do any number of things here. For example, if your -controller always needs a book ID as it's first argument, you could -have the base method capture that argument (with C<:CaptureArgs(1)>) -and use it to pull the book object with that ID from the database and -leave it in the stash for later parts of your chains to then act upon. - -In our case, let's modify our C method to first call -C. Open up C and edit the -declaration for C to match the following: + =head2 base + + Can place common logic to start chained dispatch here + + =cut + + sub base :Chained('/') :PathPart('books') :CaptureArgs(0) { + my ($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-Estash-E{resultset}> so that it's automatically available +for other actions that chain off C. 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 C<-Efind($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 +we are working with now), we will instead add that functionality +to a common C action shortly. + +As for C, let's modify it to first dispatch to C. +Open up C and edit the declaration for +C 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 | - '-------------------------------------+--------------------------------------' +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 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 method. Click the "Return to list" link, you should +find that there are now eight books shown. =head1 MANUALLY BUILDING A CREATE FORM @@ -544,17 +553,17 @@ it. Then restart the server: 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 and enter "TCP/IP Illustrated, Vol 3" for the title, a rating of 5, and an @@ -612,7 +621,7 @@ and 2) the four lines for the Delete link near the bottom). [% # Add a link to delete a book %] - Delete + Delete [% END -%] @@ -622,13 +631,94 @@ 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). -B 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). +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 @@ -642,12 +732,12 @@ following method: =cut - sub delete :Chained('base') :PathPart('delete') :Args(1) { - # $id = primary key of book to delete - my ($self, $c, $id) = @_; + sub delete :Chained('object') :PathPart('delete') :Args(0) { + my ($self, $c) = @_; - # Search for the book and then delete it - $c->model('DB::Books')->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."; @@ -656,12 +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 @@ -679,29 +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/delete/* | /books/base (0) | - | | => /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 | - '-------------------------------------+--------------------------------------' + [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 @@ -711,9 +804,11 @@ 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 @@ -726,37 +821,40 @@ 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 :Chained('base') :PathPart('delete') :Args(1) { - # $id = primary key of book to delete - my ($self, $c, $id) = @_; + sub delete :Chained('object') :PathPart('delete') :Args(0) { + my ($self, $c) = @_; - # Search for the book and then delete it - $c->model('DB::Books')->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 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. +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 @@ -774,15 +872,15 @@ method to match the following: =cut - sub delete :Chained('base') :PathPart('delete') :Args(1) { - # $id = primary key of book to delete - my ($self, $c, $id) = @_; + sub delete :Chained('object') :PathPart('delete') :Args(0) { + my ($self, $c) = @_; - # Search for the book and then delete it - $c->model('DB::Books')->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."})); } @@ -810,8 +908,9 @@ 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 Another popular method for maintaining server-side @@ -822,10 +921,10 @@ 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 +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 +that should really go to Window A. For this reason, you may wish to use the "query param" technique shown here in your applications.