=item 9
-L<Appendicies|Catalyst::Manual::Tutorial::Appendicies>
+L<Appendices|Catalyst::Manual::Tutorial::Appendices>
=back
This part of the tutorial builds on the fairly primitive application
created in Part 2 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
+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.
-B<TIP>: Note that all of the code for this part of the tutorial can be
-pulled from the Catalyst Subversion repository in one step with the
-following command:
-
- svn checkout http://dev.catalyst.perl.org/repos/Catalyst/trunk/examples/Tutorial@###
- IMPORTANT: Does not work yet. Will be completed for final version.
-
-
+You can checkout the source code for this example from the catalyst
+subversion repository as per the instructions in
+L<Catalyst::Manual::Tutorial::Intro>
=head1 FORMLESS SUBMISSION
=head2 url_create
- Create a book with the supplied title, rating and author
+ Create a book with the supplied title, rating, and author
=cut
sub url_create : Local {
- # In addition to self & context, get the title, rating & author_id args
- # from the URL. Note that Catalyst automatically puts extra information
- # after the "/<controller_name>/<action_name/" into @_
+ # In addition to self & context, get the title, rating, &
+ # author_id args from the URL. Note that Catalyst automatically
+ # puts extra information after the "/<controller_name>/<action_name/"
+ # into @_
my ($self, $c, $title, $rating, $author_id) = @_;
# 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({
- title => $title,
- rating => $rating
+ title => $title,
+ rating => $rating
});
# Add a record to the join table for this book, mapping to
[% # optional, but prevents "massive indenting" of deeply nested objects -%]
[% USE Dumper(Indent=1) -%]
- [% # Set the page title -%]
+ [% # Set the page title. META can 'go back' and set values in templates -%]
+ [% # that have been processed 'before' this template (here it's for -%]
+ [% # root/lib/site/html and root/lib/site/header). Note that META on -%]
+ [% # simple strings (e.g., no variable interpolation). -%]
[% META title = 'Book Created' %]
- [% # Output information about the record that was added. Note use -%]
- [% # of 'first' to only list the first author (if > 1 author). -%]
- <p>Added book '[% book.title %]' by '[% book.authors.first.last_name %]'
+ [% # Output information about the record that was added. First title. -%]
+ <p>Added book '[% book.title %]'
+
+ [% # Output the last name of the first author. This is complicated by an -%]
+ [% # issue in TT 2.15 where blessed hash objects are not handled right. -%]
+ [% # First, fetch 'book.authors' from the DB once. -%]
+ [% authors = book.authors %]
+ [% # Now use IF statements to test if 'authors.first' is "working". If so, -%]
+ [% # we use it. Otherwise we use a hack that seems to keep TT 2.15 happy. -%]
+ by '[% authors.first.last_name IF authors.first;
+ authors.list.first.value.last_name IF ! authors.first %]'
+
+ [% # Output the rating for the book that was added -%]
with a rating of [% book.rating %].</p>
[% # 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>
- [% # Try out the TT Dumper -%]
+ [% # Try out the TT Dumper (for development only!) -%]
<pre>
Dump of the 'book' variable:
[% Dumper.dump(book) %]
</pre>
-The TT C<USE> directive allows access to a variety of plugin modules (we
-are talking TT plugins here, 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 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>
+"pretty printing" of objects and variables. Other than that, the rest
+of the code should be familiar from the examples in Part 2.
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:
+it. Then restart the server:
$ script/myapp_server.pl
B<TIP>: You can use C<script/myapp_server.pl -r> to have the development
server auto-detect changed files and reload itself (if your browser acts
odd, you should also try throwing in a C<-k>). If you make changes to
-just the TT templates, you do not need to reload the development server
+the TT templates only, you do not need to reload the development server
(only changes to "compiled code" such as Controller and Model C<.pm>
files require a reload).
INSERT INTO books (rating, title) VALUES (?, ?): `5', `TCPIP_Illustrated_Vol-2'
INSERT INTO book_authors (author_id, book_id) VALUES (?, ?): `4', `6'
+ SELECT author.id, author.first_name, author.last_name
+ FROM book_authors me JOIN authors author
+ ON ( author.id = me.author_id ) WHERE ( me.book_id = ? ): '6'
+
+The C<INSERT> statements are obviously adding the book and linking it to
+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).
+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
+
+You should be able to click "Return to list" and now see 3 copies of
+"TCP_Illustrated_Vol-2".
=head1 MANUALLY BUILDING A CREATE FORM
$c->stash->{template} = 'books/form_create.tt2';
}
-This action merely invokes a view containing a book creation form.
-
+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 = 'Book Create' -%]
+ [% META title = 'Manual Form Book Create' -%]
<form method="post" action="[% Catalyst.uri_for('form_create_do') %]">
<table>
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 Method to Process Form Values and Update Database
+=head2 Add a Method to Process Form Values and Update Database
Edit C<lib/MyApp/Controller/Books.pm> and add the following method to
-save the form information to the databse:
+save the form information to the database:
=head2 form_create_do
# Store new model object in stash
$c->stash->{book} = $book;
- # Avoid Data::Dumper issue mention earlier
+ # Avoid Data::Dumper issue mentioned earlier
# You can probably omit this
$Data::Dumper::Useperl = 1;
=head2 Test Out The Form
-If the application is still running from before, use C<Ctrl-C> to kill it. Then restart the server:
+If the application is still running from before, use C<Ctrl-C> to kill
+it. Then restart the server:
$ script/myapp_server.pl
"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 a bit crude; we will address this concern with a drop-down
-list in Part 8.
-
+obviously crude; we will address this concern with a drop-down list in
+Part 8.
=head1 A SIMPLE DELETE FEATURE
-Turning out attention to the delete portion of CRUD, this section
+Turning our attention to the delete portion of CRUD, this section
illustrates some basic techniques that can be used to remove information
from the database.
<td>[% book.title %]</td>
<td>[% book.rating %]</td>
<td>
- [% # Print author count in parens. 'book.authors' uses the 'many_to_many' -%]
- [% # relationship to retrieve all of the authors of a book. 'size' is a -%]
- [% # TT VMethod to get the number of elements in a list. -%]
- ([% book.authors.size %])
- [% # Use an alternate form of a FOREACH loop to display authors. -%]
- [% # _ below is the TT string concatenation operator. -%]
- [% author.last_name _' ' FOREACH author = book.authors %]
- [% # Note: if many_to_many relationship not used in Authors.pm, you could -%]
- [% # have used the following to 'walk' through the 'join table objects' -%]
- [% # bk_author.author.last_name _' ' FOREACH bk_author = book.book_authors %]
+ [% # First initialize a TT variable to hold a list. Then use a TT FOREACH -%]
+ [% # loop in 'side effect notation' to load just the last names of the -%]
+ [% # authors into the list. Note that the 'push' TT vmethod does not -%]
+ [% # a value, so nothing will be printed here. But, if you have something -%]
+ [% # in TT that does return a method and you don't want it printed, you -%]
+ [% # can: 1) assign it to a bogus value, or 2) use the CALL keyword to -%]
+ [% # call it and discard the return value. -%]
+ [% tt_authors = [ ];
+ tt_authors.push(author.last_name) FOREACH author = book.authors %]
+ [% # Now use a TT 'virtual method' to display the author count in parens -%]
+ ([% tt_authors.size %])
+ [% # Use another TT vmethod to join & print the names & comma separators -%]
+ [% tt_authors.join(', ') %]
</td>
<td>
[% # Add a link to delete a book %]
right side of the table with a C<Delete> "button" (for simplicity, links
will be used instead of full HTML buttons).
-
=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
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.
+C<book_authors>, C<delete> does not (only use C<delete_all> if you
+really need the cascading deletes... otherwise you are wasting resources).
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
completed, C<detach> does I<not> return. Other than that, the two are
equivalent.
-Another alternative to C<forward> would be to use
-C<$c-E<gt>response-E<gt>redirect($c-E<gt>uri_for('/books/list'))>. The
-C<forward> and C<redirect> operations differ in several important
-respects that stem from the fact that redirects cause the client browser
-to issue an entirely new HTTP request. In doing so, this results in a
-new URL showing in the browser window. And, because the stash
-information is reset for every request, the "Book deleted" message would
-not be displayed.
-
=head2 Try the Delete Feature
$ script/myapp_server.pl
Then point your browser to L<http://localhost:3000/books/list> and click
-the "Delete" link next to "TCPIP_Illustrated_Vol-2". A green "Book
-deleted" status message should display at the top of the page, along
-with a list of the six remaining books.
+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.
+
+
+=head2 Fixing a Dangerous URL
+
+Note the URL in your browser once you have performed the deleted in the
+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.
+
+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
+new request. As a result, the URL in the browser is updated to match
+the destination of the redirection URL.
+
+To convert the forward used in the previous section to a redirect,
+open C<lib/MyApp/Controller/Books.pm> and the existing C<sub delete>
+method to match:
+
+ =head2 delete
+
+ Delete a book
+
+ =cut
+
+ sub delete : Local {
+ # $id = primary key of book to delete
+ my ($self, $c, $id) = @_;
+
+ # Search for the book and then delete it
+ $c->model('MyAppDB::Book')->search({id => $id})->delete_all;
+
+ # 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'));
+ }
+
+
+=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, 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 the redirect itself. Open
+C<lib/MyApp/Controller/Books.pm> and update the existing
+C<sub delete> method to match the following:
+
+ =head2 delete
+
+ Delete a book
+
+ =cut
+
+ sub delete : Local {
+ # $id = primary key of book to delete
+ my ($self, $c, $id) = @_;
+
+ # Search for the book and then delete it
+ $c->model('MyAppDB::Book')->search({id => $id})->delete_all;
+
+ # Redirect the user back to the list page with status msg as an arg
+ $c->response->redirect($c->uri_for('/books/list',
+ {status_msg => "Book deleted."}));
+ }
+
+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
+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>
+
+
+=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> and 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 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).
=head1 AUTHOR
Kennedy Clark, C<hkclark@gmail.com>
-Please report any errors, issues or suggestions to the 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-Runtime/lib/Catalyst/Manual/Tutorial/>.
Copyright 2006, Kennedy Clark, under Creative Commons License
(L<http://creativecommons.org/licenses/by-nc-sa/2.5/>).
-Version: .94
-
projects / catagits/Catalyst-Runtime.git / blobdiff