=head1 NAME
-Catalyst::Manual::Tutorial::BasicCRUD - Catalyst Tutorial Part 3: Basic CRUD
-
+Catalyst::Manual::Tutorial::BasicCRUD - Catalyst Tutorial - Part 3: Basic CRUD
=head1 OVERVIEW
This is B<Part 3 of 9> for the Catalyst tutorial.
-L<Totorial Overview|Catalyst::Manual::Tutorial>
+L<Tutorial Overview|Catalyst::Manual::Tutorial>
=over 4
=item 9
-L<Appendicies|Catalyst::Manual::Tutorial::Appendicies>
+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 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.
-
-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.
-
+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
+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.
+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
-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
=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
$c->stash->{template} = 'books/create_done.tt2';
}
-Notice that Catalyst takes "extra slash-separated information" from the URL and passes it as arguments in C<@_>. The C<url_create> action then uses a simple call to the DBIC C<create> method to add the requested information to the database (with a separate call to C<add_to_book_authors> to update the join table). As do virtually all controller methods (at least the ones that directly handle user input), it then sets the template that should handle this request.
+Notice that Catalyst takes "extra slash-separated information" from the
+URL and passes it as arguments in C<@_>. The C<url_create> action then
+uses a simple call to the DBIC C<create> method to add the requested
+information to the database (with a separate call to
+C<add_to_book_authors> to update the join table). As do virtually all
+controller methods (at least the ones that directly handle user input),
+it then sets the template that should handle this request.
=head2 Include a Template for the C<url_create> Action:
[% # 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.
-
-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>.
+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:
+If the application is still running from before, use C<Ctrl-C> to kill
+it. Then restart the server:
$ script/myapp_server.pl
-Note that new path for C</books/url_create> appears in the startup debug output.
+Note that new path for C</books/url_create> appears in the startup debug
+output.
-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 (only changes to "compiled code" such as Controller and Model C<.pm> files require a reload).
+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
+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).
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. You should also see the following DBIC debug messages displayed
+in the development server log messages:
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).
+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
-Although the C<url_create> action in the previous step does begin to reveal the power and flexibility of both Catalyst and DBIC, it's obviously not a very realistic example of how users should be expected to enter data. This section begins to address that concern.
+Although the C<url_create> action in the previous step does begin to
+reveal the power and flexibility of both Catalyst and DBIC, it's
+obviously not a very realistic example of how users should be expected
+to enter data. This section begins to address that concern.
=head2 Add Method to Display The 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>
<input type="submit" name="Submit" value="Submit">
</form>
-Note that we have specified the target of the form data as C<form_create_do>, the method created in the section that follows.
-
+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:
+Edit C<lib/MyApp/Controller/Books.pm> and add the following method to
+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
-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 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 a bit crude; we will address this concern with a drop-down list in Part 8.
+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
+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.
=head1 A SIMPLE DELETE FEATURE
-Turning out attention to the delete portion of CRUD, this section illustrates some basic techniques that can be used to remove information from the database.
+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.
=head2 Include a Delete Link in the List
-Edit C<root/src/books/list.tt2> and update it to the following (two sections have changed: 1) the additional '<th>Links</th>' table header, and 2) the four lines for the Delete link near the bottom).
+Edit C<root/src/books/list.tt2> and update it to the following (two
+sections have changed: 1) the additional '<th>Links</th>' table header,
+and 2) the four lines for the Delete link near the bottom).
[% # This is a TT comment. The '-' at the end "chomps" the newline. You won't -%]
[% # see this "chomping" in your browser because HTML ignores blank lines, but -%]
<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 %]
[% 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).
=head2 Add a Delete Action to the Controller
-Open C<lib/MyApp/Controller/Books.pm> in your editor and add the following method:
+Open C<lib/MyApp/Controller/Books.pm> in your editor and add the
+following method:
- =head2 Delete
+ =head2 delete
Delete a book
$c->forward('list');
}
-This method first deletes the book with the specified primary key ID. However, it also removes the corresponding entry from the C<book_authors> table. Note that C<delete_all> was used instead of C<delete>: whereas C<delete_all> also removes the join table entries in C<book_authors>, C<delete> does not.
+This method first deletes the book with the specified primary key ID.
+However, it also removes the corresponding entry from the
+C<book_authors> table. Note that C<delete_all> was used instead of
+C<delete>: whereas C<delete_all> also removes the join table entries in
+C<book_authors>, C<delete> does not (only use C<delete_all> if you
+really need the cascading deletes... otherwise you are wasting resources).
-Then, rather than forwarding to a "delete done" page as we did with the earlier create example, it simply sets the C<status_msg> to display a notification to the user as the normal list view is rendered.
+Then, rather than forwarding to a "delete done" page as we did with the
+earlier create example, it simply sets the C<status_msg> to display a
+notification to the user as the normal list view is rendered.
-The C<delete> action uses the context C<forward> method to return the user to the book list. The C<detach> method could have also been used. Whereas C<forward> I<returns> to the original action once it is completed, C<detach> does I<not> return. Other than that, the two are equivalent.
-
-Another alternative to C<forward> would be to use C<$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.
+The C<delete> action uses the context C<forward> method to return the
+user to the book list. The C<detach> method could have also been used.
+Whereas C<forward> I<returns> to the original action once it is
+completed, C<detach> does I<not> return. Other than that, the two are
+equivalent.
=head2 Try the Delete Feature
-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
-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.
+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.
+=head2 Fixing a Dangerous URL
-=head1 AUTHOR
+Note the URL in your browser once you have performed the deleted in the
+prior step -- it is still referencing the delete action:
-Kennedy Clark, C<hkclark@gmail.com>
+ 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 edit 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 (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
-Please report any errors, issues or suggestions to the author.
+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:
-Copyright 2006, Kennedy Clark. All rights reserved.
+ =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>. 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).
+
+
+=head1 AUTHOR
+
+Kennedy Clark, C<hkclark@gmail.com>
-This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
+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/>.
-Version: .94
+Copyright 2006, Kennedy Clark, under Creative Commons License
+(L<http://creativecommons.org/licenses/by-nc-sa/2.5/>).
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