=head1 DESCRIPTION
This chapter of the tutorial builds on the fairly primitive application
-created in Chapter 3 to add basic support for Create, Read, Update, and
-Delete (CRUD) of C<Book> objects. Note that the 'list' function in
-Chapter 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
-Chapter 9.
+created in
+L<Chapter 3|Catalyst::Manual::Tutorial::03_MoreCatalystBasics> to add
+basic support for Create, Read, Update, and Delete (CRUD) of C<Book>
+objects. Note that the 'list' function in
+L<Chapter 3|Catalyst::Manual::Tutorial::03_MoreCatalystBasics> 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
+L<Chapter 9|Catalyst::Manual::Tutorial::09_AdvancedCRUD>.
Although this chapter of the tutorial will show you how to build CRUD
functionality yourself, another option is to use a "CRUD builder" type
quick and easy. For example, see L<Catalyst::Plugin::AutoCRUD>,
L<CatalystX::CRUD>, and L<CatalystX::CRUD::YUI>.
-You can check out the source code for this example from the Catalyst
-Subversion repository as per the instructions in
+Source code for the tutorial in included in the F</home/catalyst/Final>
+directory of the Tutorial Virtual machine (one subdirectory per
+chapter). There are also instructions for downloading the code in
L<Catalyst::Manual::Tutorial::01_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
+feature of Catalyst (we will employ the more common form-based
submission in the sections that follow).
Edit C<lib/MyApp/Controller/Books.pm> and enter the following method:
=head2 url_create
-
+
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 @_. The args are separated by the '/' char on the URL.
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('DB::Book')->create({
title => $title,
rating => $rating
});
-
+
# Add a record to the join table for this book, mapping to
# appropriate author
$book->add_to_book_authors({author_id => $author_id});
# Note: Above is a shortcut for this:
# $book->create_related('book_authors', {author_id => $author_id});
-
+
# Assign the Book object to the stash for display and set template
$c->stash(book => $book,
template => 'books/create_done.tt2');
+
+ # Disable caching for this page
+ $c->response->header('Cache-Control' => 'no-cache');
}
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.
+URL and passes it as arguments in C<@_> (as long as the number of
+arguments is not "fixed" using an attribute like C<:Args(0)>). 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.
+
+Also note that we are explicitly setting a C<no-cache> "Cache-Control"
+header to force browsers using the page to get a fresh copy every time.
+You could even move this to a C<auto> method in
+C<lib/MyApp/Controller/Root.pm> and it would automatically get applied
+to every page in the whole application via a single line of code
+(remember from Chapter 3, that every C<auto> method gets run in the
+Controller hierarchy).
=head2 Include a Template for the 'url_create' Action:
[% # Not a good idea for production use, though. :-) 'Indent=1' is -%]
[% # optional, but prevents "massive indenting" of deeply nested objects -%]
[% USE Dumper(Indent=1) -%]
-
+
[% # 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 only -%]
- [% # works on simple/static strings (i.e. there is no variable -%]
- [% # interpolation). -%]
+ [% # that have been processed 'before' this template (here it's updating -%]
+ [% # the title in the root/src/wrapper.tt2 wrapper template). Note that -%]
+ [% # META only works on simple/static strings (i.e. there is no variable -%]
+ [% # interpolation -- if you need dynamic/interpolated content in your -%]
+ [% # title, set "$c->stash(title => $something)" in the controller). -%]
[% META title = 'Book Created' %]
-
+
[% # Output information about the record that was added. First title. -%]
<p>Added book '[% book.title %]'
-
- [% # Output the last name of the first author. -%]
+
+ [% # Then, output the last name of the first author -%]
by '[% book.authors.first.last_name %]'
-
- [% # Output the rating for the book that was added -%]
+
+ [% # Then, output the rating for the book that was added -%]
with a rating of [% book.rating %].</p>
-
- [% # Provide a link back to the list page -%]
- [% # 'uri_for()' builds a full URI; e.g., 'http://localhost:3000/books/list' -%]
+
+ [% # Provide a link back to the list page. 'c.uri_for' builds -%]
+ [% # a full URI; e.g., 'http://localhost:3000/books/list' -%]
<p><a href="[% c.uri_for('/books/list') %]">Return to list</a></p>
-
+
[% # Try out the TT Dumper (for development only!) -%]
<pre>
Dump of the 'book' variable:
"pretty printing" of objects and variables. Other than that, the rest
of the code should be familiar from the examples in Chapter 3.
-Note: If you are using TT v2.15 you will need to change the code that
-outputs the "last name for the first author" above to match this:
-
- [% authors = book.authors %]
- by '[% authors.first.last_name IF authors.first;
- authors.list.first.value.last_name IF ! authors.first %]'
-
-to get around an issue in TT v2.15 where blessed hash objects were not
-handled correctly. But, if you are still using v2.15, it's probably
-time to upgrade (v2.15 is almost 4 years old). If you are following
-along in Debian, then you should be on at least v2.20. You can test
-your version of Template Toolkit with the following:
-
- perl -MTemplate -e 'print "$Template::VERSION\n"'
-
=head2 Try the 'url_create' Feature
browser at the C</books/list> page). You should now see the six DBIC
debug messages similar to the following (where N=1-6):
- SELECT author.id, author.first_name, author.last_name
- FROM book_author me JOIN author author
+ SELECT author.id, author.first_name, author.last_name
+ FROM book_author me JOIN author author
ON author.id = me.author_id WHERE ( me.book_id = ? ): 'N'
sub url_create :Chained('/') :PathPart('books/url_create') :Args(3) {
# In addition to self & context, get the title, rating, &
# author_id args from the URL. Note that Catalyst automatically
- # puts the first 3 arguments worth of extra information after the
+ # puts the first 3 arguments worth of extra information after the
# "/<controller_name>/<action_name/" into @_ because we specified
# "Args(3)". The args are separated by the '/' char on the URL.
my ($self, $c, $title, $rating, $author_id) = @_;
-
+
...
This converts the method to take advantage of the Chained
| /books/url_create | /books/url_create |
'-------------------------------------+--------------------------------------'
-When the development server restarts, the debug output should change to
-something along the lines of the following:
+When the development server restarts after our conversion to Chained
+dispatch, the debug output should change to something along the lines of
+the following:
[debug] Loaded Path actions:
.-------------------------------------+--------------------------------------.
| /books | /books/index |
| /books/list | /books/list |
'-------------------------------------+--------------------------------------'
-
+
[debug] Loaded Chained actions:
.-------------------------------------+--------------------------------------.
| Path Spec | Private |
method:
=head2 base
-
+
Can place common logic to start chained dispatch here
-
+
=cut
-
+
sub base :Chained('/') :PathPart('books') :CaptureArgs(0) {
my ($self, $c) = @_;
-
+
# Store the ResultSet in stash so it's available for other methods
$c->stash(resultset => $c->model('DB::Book'));
-
+
# 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
+C<< $c->stash->{resultset} >> so that it's automatically available
for other actions that chain off C<base>. If your controller always
needs a book ID as its first argument, you could have the base method
capture that argument (with C<:CaptureArgs(1)>) and use it to pull the
-book object with C<-E<gt>find($id)> and leave it in the stash for later
+book object with C<< ->find($id) >> and leave it in the stash for later
parts of your chains to then act upon. Because we have several actions
that don't need to retrieve a book (such as the C<url_create> we are
working with now), we will instead add that functionality to a common
Although the C<url_create> action in the previous step does begin to
reveal the power and flexibility of both Catalyst and DBIC, it's
obviously not a very realistic example of how users should be expected
-to enter data. This section begins to address that concern.
+to enter data. This section begins to address that concern (but just
+barely, see L<Chapter 9|Catalyst::Manual::Tutorial::09_AdvancedCRUD>
+for better options for handling web-based forms).
=head2 Add Method to Display The Form
Edit C<lib/MyApp/Controller/Books.pm> and add the following method:
=head2 form_create
-
+
Display form to collect information for book to create
-
+
=cut
-
+
sub form_create :Chained('base') :PathPart('form_create') :Args(0) {
my ($self, $c) = @_;
-
+
# Set the TT template to use
$c->stash(template => 'books/form_create.tt2');
}
Open C<root/src/books/form_create.tt2> in your editor and enter:
[% META title = 'Manual Form Book Create' -%]
-
+
<form method="post" action="[% c.uri_for('form_create_do') %]">
<table>
<tr><td>Title:</td><td><input type="text" name="title"></td></tr>
save the form information to the database:
=head2 form_create_do
-
+
Take information from form and add to database
-
+
=cut
-
+
sub form_create_do :Chained('base') :PathPart('form_create_do') :Args(0) {
my ($self, $c) = @_;
-
+
# Retrieve the values from the form
my $title = $c->request->params->{title} || 'N/A';
my $rating = $c->request->params->{rating} || 'N/A';
my $author_id = $c->request->params->{author_id} || '1';
-
+
# Create the book
my $book = $c->model('DB::Book')->create({
title => $title,
$book->add_to_book_authors({author_id => $author_id});
# Note: Above is a shortcut for this:
# $book->create_related('book_authors', {author_id => $author_id});
-
- # Avoid Data::Dumper issue mentioned earlier
- # You can probably omit this
- $Data::Dumper::Useperl = 1;
-
+
# Store new model object in stash and set template
$c->stash(book => $book,
template => 'books/create_done.tt2');
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 and
-add validation to our forms in Chapter 9.
+add validation to our forms in
+L<Chapter 9|Catalyst::Manual::Tutorial::09_AdvancedCRUD>.
=head1 A SIMPLE DELETE FEATURE
Edit C<root/src/books/list.tt2> and update it to match 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 -%]
- [% # it WILL eliminate a blank line if you view the HTML source. It's purely -%]
- [%- # optional, but both the beginning and the ending TT tags support chomping. -%]
-
- [% # Provide a title -%]
+header, and 2) the five lines for the Delete link near the bottom):
+
+ [% # This is a TT comment. -%]
+
+ [%- # Provide a title -%]
[% META title = 'Book List' -%]
-
+
+ [% # Note That the '-' at the beginning or end of TT code -%]
+ [% # "chomps" the whitespace/newline at that end of the -%]
+ [% # output (use View Source in browser to see the effect) -%]
+
+ [% # Some basic HTML with a loop to display books -%]
<table>
<tr><th>Title</th><th>Rating</th><th>Author(s)</th><th>Links</th></tr>
[% # Display each book in a table row %]
<td>[% book.title %]</td>
<td>[% book.rating %]</td>
<td>
- [% # NOTE: See "Exploring The Power of DBIC" for a better way to do this! -%]
+ [% # NOTE: See Chapter 4 for a better way to do this! -%]
[% # 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 doesn't return -%]
[% # a value, so nothing will be printed here. But, if you have something -%]
- [% # in TT that does return a value and you don't want it printed, you can -%]
+ [% # in TT that does return a value and you don't want it printed, you -%]
[% # 1) assign it to a bogus value, or -%]
[% # 2) use the CALL keyword to call it and discard the return value. -%]
[% tt_authors = [ ];
</td>
<td>
[% # Add a link to delete a book %]
- <a href="[% c.uri_for(c.controller.action_for('delete'), [book.id]) %]">Delete</a>
+ <a href="[%
+ c.uri_for(c.controller.action_for('delete'), [book.id]) %]">Delete</a>
</td>
</tr>
[% END -%]
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; in practice, anything that
-modifies data should be handled with a form sending a POST request).
+will be used instead of full HTML buttons; but, in practice, anything
+that modifies data should be handled with a form sending a POST
+request).
Also notice that we are using a more advanced form of C<uri_for> than we
-have seen before. Here we use C<$c-E<gt>controller-E<gt>action_for> to
+have seen before. Here we use C<< $c->controller->action_for >> to
automatically generate a URI appropriate for that action based on the
method we want to link to while inserting the C<book.id> value into the
appropriate place. Now, if you ever change C<:PathPart('delete')> in
-your controller method to C<:PathPart('kill')>, then your links will
-automatically update without any changes to your .tt2 template file. As
-long as the name of your method does not change (here, "delete"), then
-your links will still be correct. There are a few shortcuts and options
-when using C<action_for()>:
+your controller method to something like C<:PathPart('kill')>, then your
+links will automatically update without any changes to your .tt2
+template file. As long as the name of your method does not change
+(here, "delete"), then your links will still be correct. There are a
+few shortcuts and options when using C<action_for()>:
=over 4
=item *
If you are referring to a method in the current controller, you can use
-C<$self-E<gt>action_for('_method_name_')>.
+C<< $self->action_for('_method_name_') >>.
=item *
If you are referring to a method in a different controller, you need to
include that controller's name as an argument to C<controller()>, as in
-C<$c-E<gt>controller('_controller_name_')-E<gt>action_for('_method_name_')>.
+C<< $c->controller('_controller_name_')->action_for('_method_name_') >>.
=back
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};
-
+
# Print a message to the debug log
$c->log->debug("*** INSIDE OBJECT METHOD for obj id=$id ***");
}
Now, any other method that chains off C<object> will automatically have
-the appropriate book waiting for it in C<$c-E<gt>stash-E<gt>{object}>.
+the appropriate book waiting for it in C<< $c->stash->{object} >>.
=head2 Add a Delete Action to the Controller
following method:
=head2 delete
-
+
Delete a book
-
+
=cut
-
+
sub delete :Chained('object') :PathPart('delete') :Args(0) {
my ($self, $c) = @_;
-
+
# Use the book object saved by 'object' and delete it along
# with related 'book_author' entries
$c->stash->{object}->delete;
-
+
# Set a status message to be displayed at the top of the view
$c->stash->{status_msg} = "Book deleted.";
-
+
# Forward to the list action/method in this controller
$c->forward('list');
}
SELECT me.id, me.title, me.rating FROM book me WHERE ( ( me.id = ? ) ): '6'
DELETE FROM book WHERE ( id = ? ): '6'
- SELECT me.book_id, me.author_id FROM book_author me WHERE ( me.book_id = ? ): '6'
- DELETE FROM book_author WHERE ( author_id = ? AND book_id = ? ): '4', '6'
+If you get the error C<file error - books/delete.tt2: not found> then you
+probably forgot to uncomment the template line in C<sub list> at the end of
+chapter 3.
=head2 Fixing a Dangerous URL
What if the user were to press reload with this URL still active? In
this case the redundant delete is harmless (although it does generate an
exception screen, it doesn't perform any undesirable actions on the
-application or database), but in other cases this could clearly be
-extremely dangerous.
+application or database), but in other cases this could clearly lead to
+trouble.
We can improve the logic by converting to a redirect. Unlike
-C<$c-E<gt>forward('list'))> or C<$c-E<gt>detach('list'))> that perform a
+C<< $c->forward('list')) >> or C<< $c->detach('list')) >> that perform a
server-side alteration in the flow of processing, a redirect is a
client-side mechanism that causes the browser to issue an entirely new
request. As a result, the URL in the browser is updated to match the
method to match:
=head2 delete
-
+
Delete a book
-
+
=cut
-
+
sub delete :Chained('object') :PathPart('delete') :Args(0) {
my ($self, $c) = @_;
-
+
# Use the book object saved by 'object' and delete it along
# with related 'book_author' 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. Note the use
# of $self->action_for as earlier in this section (BasicCRUD)
$c->response->redirect($c->uri_for($self->action_for('list')));
improvement, but notice that I<no green "Book deleted" status message is
displayed>. Because the stash is reset on every request (and a redirect
involves a second request), the C<status_msg> is cleared before it can
-be displayed.
+be displayed.
=head2 Using 'uri_for' to Pass Query Parameters
There are several ways to pass information across a redirect. One option
-is to use the C<flash> technique that we will see in Chapter 5 of this
+is to use the C<flash> technique that we will see in
+L<Chapter 5|Catalyst::Manual::Tutorial::05_Authentication> of this
tutorial; however, here we will pass the information via query
parameters on the redirect itself. Open
C<lib/MyApp/Controller/Books.pm> and update the existing C<sub delete>
method to match the following:
=head2 delete
-
+
Delete a book
-
+
=cut
-
+
sub delete :Chained('object') :PathPart('delete') :Args(0) {
my ($self, $c) = @_;
-
+
# Use the book object saved by 'object' and delete it along
# with related 'book_author' 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($self->action_for('list'),
{status_msg => "Book deleted."}));
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.
+to add "C<|| c.request.params.status_msg>" to the
+C<< <span class="message"> >> line. Note that we definitely want
+the "C<| html>" TT filter here since it would be easy for users to
+modify the message on the URL and possibly inject harmful code into the
+application if we left that off.
=head2 Try the Delete and Redirect With Query Param Logic
(and it correctly shows it without the "Book deleted" message on
redisplay).
-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 chapter of the tutorial,
-L<Authentication|Catalyst::Manual::Tutorial::05_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.
+B<NOTE:> Be sure to check out
+L<Authentication|Catalyst::Manual::Tutorial::05_Authentication> where we
+use an improved technique that is better suited to your real world
+applications.
=head1 EXPLORING THE POWER OF DBIC
In this section we will explore some additional capabilities offered by
-DBIx::Class. Although these features have relatively little to do with
-Catalyst per se, you will almost certainly want to take advantage of
-them in your applications.
+L<DBIx::Class>. Although these features have relatively little to do
+with Catalyst per se, you will almost certainly want to take advantage
+of them in your applications.
=head2 Add Datetime Columns to Our Existing Books Table
sqlite> .quit
$
+Here are the commands without the surrounding sqlite3 prompt and output
+in case you want to cut and paste them as a single block (but still
+start sqlite3 before you paste these in):
+
+ ALTER TABLE book ADD created TIMESTAMP;
+ ALTER TABLE book ADD updated TIMESTAMP;
+ UPDATE book SET created = DATETIME('NOW'), updated = DATETIME('NOW');
+ SELECT * FROM book;
+
This will modify the C<books> table to include the two new fields and
populate those fields with the current time.
$ script/myapp_create.pl model DB DBIC::Schema MyApp::Schema \
create=static components=TimeStamp dbi:SQLite:myapp.db \
on_connect_do="PRAGMA foreign_keys = ON"
- exists "/root/dev/MyApp/script/../lib/MyApp/Model"
- exists "/root/dev/MyApp/script/../t"
- Dumping manual schema for MyApp::Schema to directory /root/dev/MyApp/script/../lib ...
+ exists "/home/catalyst/dev/MyApp/script/../lib/MyApp/Model"
+ exists "/home/catalyst/dev/MyApp/script/../t"
+ Dumping manual schema for MyApp::Schema to directory /home/catalyst/dev/MyApp/script/../lib ...
Schema dump completed.
- exists "/root/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
+ exists "/home/catalyst/dev/MyApp/script/../lib/MyApp/Model/DB.pm"
Notice that we modified our use of the helper slightly: we told it to
include the L<DBIx::Class::TimeStamp> in the C<load_components> line of
relationships we manually added below the "C<# DO NOT MODIFY...>" line
were automatically preserved.
-While we have this file open, let's update it with some additional
-information to have DBIC automatically handle the updating of these two
-fields for us. Insert the following code at the bottom of the file (it
-B<must> be B<below> the "C<# DO NOT MODIFY...>" line and B<above> the
-C<1;> on the last line):
+While we C<lib/MyApp/Schema/Result/Book.pm> open, let's update it with
+some additional information to have DBIC automatically handle the
+updating of these two fields for us. Insert the following code at the
+bottom of the file (it B<must> be B<below> the "C<# DO NOT MODIFY...>"
+line and B<above> the C<1;> on the last line):
#
# Enable automatic date handling
C<set_on_update> options will cause DBIx::Class to automatically update
the timestamps in these columns whenever a row is created or modified.
+B<Note> that adding the lines above will cause the development server to
+automatically restart if you are running it with the "-r" option. In
+other words, the development server is smart enough to restart not only
+for code under the C<MyApp/Controller/>, C<MyApp/Model/>, and
+C<MyApp/View/> directories, but also under other directions such as our
+"external DBIC model" in C<MyApp/Schema/>. However, also note that it's
+smart enough to B<not> restart when you edit your C<.tt2> files under
+C<root/>.
+
Then enter the following URL into your web browser:
http://localhost:3000/books/url_create/TCPIP_Illustrated_Vol-2/5/4
-You should get the same "Book Created" screen we saw above. However, if
+You should get the same "Book Created" screen we saw earlier. However, if
you now use the sqlite3 command-line tool to dump the C<books> table,
you will see that the new book we added has an appropriate date and time
entered for it (see the last line in the listing below):
5|Designing with Web Standards|5|2010-02-16 04:15:45|2010-02-16 04:15:45
9|TCP/IP Illustrated, Vol 3|5|2010-02-16 04:15:45|2010-02-16 04:15:45
10|TCPIP_Illustrated_Vol-2|5|2010-02-16 04:18:42|2010-02-16 04:18:42
- sqlite> .q
Notice in the debug log that the SQL DBIC generated has changed to
incorporate the datetime logic:
- INSERT INTO book ( created, rating, title, updated ) VALUES ( ?, ?, ?, ? ):
+ INSERT INTO book ( created, rating, title, updated ) VALUES ( ?, ?, ?, ? ):
'2010-02-16 04:18:42', '5', 'TCPIP_Illustrated_Vol-2', '2010-02-16 04:18:42'
INSERT INTO book_author ( author_id, book_id ) VALUES ( ?, ? ): '4', '10'
An often overlooked but extremely powerful features of DBIC is that it
allows you to supply your own subclasses of C<DBIx::Class::ResultSet>.
-It allows you to pull complex and unsightly "query code" out of your
+This can be used to pull complex and unsightly "query code" out of your
controllers and encapsulate it in a method of your ResultSet Class.
These "canned queries" in your ResultSet Class can then be invoked via a
single call, resulting in much cleaner and easier to read controller
-code.
+code (or View code, if that's where you want to call it).
To illustrate the concept with a fairly simple example, let's create a
method that returns books added in the last 10 minutes. Start by making
Then open C<lib/MyApp/Schema/ResultSet/Book.pm> and enter the following:
package MyApp::Schema::ResultSet::Book;
-
+
use strict;
use warnings;
use base 'DBIx::Class::ResultSet';
-
+
=head2 created_after
-
+
A predefined search for recently added books
-
+
=cut
-
+
sub created_after {
my ($self, $datetime) = @_;
-
+
my $date_str = $self->result_source->schema->storage
->datetime_parser->format_datetime($datetime);
-
+
return $self->search({
created => { '>' => $date_str }
});
}
-
+
1;
Then add the following method to the C<lib/MyApp/Controller/Books.pm>:
=head2 list_recent
-
+
List recently created books
-
+
=cut
-
+
sub list_recent :Chained('base') :PathPart('list_recent') :Args(1) {
my ($self, $c, $mins) = @_;
-
+
# Retrieve all of the book records as book model objects and store in the
# stash where they can be accessed by the TT template, but only
# retrieve books created within the last $min number of minutes
$c->stash(books => [$c->model('DB::Book')
->created_after(DateTime->now->subtract(minutes => $mins))]);
-
+
# Set the TT template to use. You will almost always want to do this
# in your action methods (action methods respond to user input in
# your controllers).
=head2 Chaining ResultSets
-One of the most helpful and powerful features in DBIx::Class is that it
-allows you to "chain together" a series of queries (note that this has
-nothing to do with the "Chained Dispatch" for Catalyst that we were
-discussing above). Because each ResultSet returns another ResultSet,
-you can take an initial query and immediately feed that into a second
-query (and so on for as many queries you need). Note that no matter how
-many ResultSets you chain together, the database itself will not be hit
-until you use a method that attempts to access the data. And, because
-this technique carries over to the ResultSet Class feature we
+One of the most helpful and powerful features in C<DBIx::Class> is that
+it allows you to "chain together" a series of queries (note that this
+has nothing to do with the "Chained Dispatch" for Catalyst that we were
+discussing earlier). Because each ResultSet method returns another
+ResultSet, you can take an initial query and immediately feed that into
+a second query (and so on for as many queries you need). Note that no
+matter how many ResultSets you chain together, the database itself will
+not be hit until you use a method that attempts to access the data. And,
+because this technique carries over to the ResultSet Class feature we
implemented in the previous section for our "canned search", we can
combine the two capabilities. For example, let's add an action to our
C<Books> controller that lists books that are both recent I<and> have
the following method:
=head2 list_recent_tcp
-
+
List recently created books
-
+
=cut
-
+
sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
my ($self, $c, $mins) = @_;
-
+
# Retrieve all of the book records as book model objects and store in the
# stash where they can be accessed by the TT template, but only
# retrieve books created within the last $min number of minutes
# AND that have 'TCP' in the title
- $c->stash(books => [$c->model('DB::Book')
- ->created_after(DateTime->now->subtract(minutes => $mins))
- ->search({title => {'like', '%TCP%'}})
- ]);
-
+ $c->stash(books => [
+ $c->model('DB::Book')
+ ->created_after(DateTime->now->subtract(minutes => $mins))
+ ->search({title => {'like', '%TCP%'}})
+ ]);
+
# Set the TT template to use. You will almost always want to do this
# in your action methods (action methods respond to user input in
# your controllers).
Take a look at the DBIC_TRACE output in the development server log for
the first URL and you should see something similar to the following:
- SELECT me.id, me.title, me.rating, me.created, me.updated FROM book me
+ SELECT me.id, me.title, me.rating, me.created, me.updated FROM book me
WHERE ( ( title LIKE ? AND created > ? ) ): '%TCP%', '2010-02-16 02:49:32'
However, let's not pollute our controller code with this raw "TCP" query
and add the following method:
=head2 title_like
-
+
A predefined search for books with a 'LIKE' search in the string
-
+
=cut
-
+
sub title_like {
my ($self, $title_str) = @_;
-
+
return $self->search({
title => { 'like' => "%$title_str%" }
});
We defined the search string as C<$title_str> to make the method more
flexible. Now update the C<list_recent_tcp> method in
C<lib/MyApp/Controller/Books.pm> to match the following (we have
-replaced the C<-E<gt>search> line with the C<-E<gt>title_like> line
+replaced the C<< ->search >> line with the C<< ->title_like >> line
shown here -- the rest of the method should be the same):
=head2 list_recent_tcp
-
+
List recently created books
-
+
=cut
-
+
sub list_recent_tcp :Chained('base') :PathPart('list_recent_tcp') :Args(1) {
my ($self, $c, $mins) = @_;
-
+
# Retrieve all of the book records as book model objects and store in the
# stash where they can be accessed by the TT template, but only
# retrieve books created within the last $min number of minutes
# AND that have 'TCP' in the title
- $c->stash(books => [$c->model('DB::Book')
- ->created_after(DateTime->now->subtract(minutes => $mins))
- ->title_like('TCP')
- ]);
-
+ $c->stash(books => [
+ $c->model('DB::Book')
+ ->created_after(DateTime->now->subtract(minutes => $mins))
+ ->title_like('TCP')
+ ]);
+
# Set the TT template to use. You will almost always want to do this
# in your action methods (action methods respond to user input in
# your controllers).
#
sub full_name {
my ($self) = @_;
-
+
return $self->first_name . ' ' . $self->last_name;
}
C<lib/MyApp/Schema/Result/Book.pm> and add the following method:
=head2 author_count
-
+
Return the number of authors for the current book
-
+
=cut
-
+
sub author_count {
my ($self) = @_;
-
+
# Use the 'many_to_many' relationship to fetch all of the authors for the current
# and the 'count' method in DBIx::Class::ResultSet to get a SQL COUNT
return $self->authors->count;
same C<lib/MyApp/Schema/Result/Book.pm> file:
=head2 author_list
-
+
Return a comma-separated list of authors for the current book
-
+
=cut
-
+
sub author_list {
my ($self) = @_;
-
- # Loop through all authors for the current book, calling all the 'full_name'
+
+ # Loop through all authors for the current book, calling all the 'full_name'
# Result Class method for each
my @names;
foreach my $author ($self->authors) {
push(@names, $author->full_name);
}
-
+
return join(', ', @names);
}
Although most of the code we removed comprised comments, the overall
effect is dramatic... because our view code is so simple, we don't need
-huge comments to clue people in to the gist of our code. The view code
+huge comments to clue people in to the gist of our code. The view code
is now self-documenting and readable enough that you could probably get
-by with no comments at all. All of the "complex" work is being done in
+by with no comments at all. All of the "complex" work is being done in
our Result Class methods (and, because we have broken the code into
nice, modular chunks, the Result Class code is hardly something you
would call complex).
As we saw in this section, always strive to keep your view AND
controller code as simple as possible by pulling code out into your
-model objects. Because DBIx::Class can be easily extended in so many
+model objects. Because L<DBIx::Class> can be easily extended in so many
ways, it's an excellent to way accomplish this objective. It will make
your code cleaner, easier to write, less error-prone, and easier to
debug and maintain.
down.
+You can jump to the next chapter of the tutorial here:
+L<Authentication|Catalyst::Manual::Tutorial::05_Authentication>
+
+
=head1 AUTHOR
Kennedy Clark, C<hkclark@gmail.com>
Feel free to contact the author for any errors or suggestions, but the
best way to report issues is via the CPAN RT Bug system at
-<https://rt.cpan.org/Public/Dist/Display.html?Name=Catalyst-Manual>.
-
-The most recent version of the Catalyst Tutorial can be found at
-L<http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.80/trunk/lib/Catalyst/Manual/Tutorial/>.
+L<https://rt.cpan.org/Public/Dist/Display.html?Name=Catalyst-Manual>.
-Copyright 2006-2010, Kennedy Clark, under the
+Copyright 2006-2011, Kennedy Clark, under the
Creative Commons Attribution Share-Alike License Version 3.0
(L<http://creativecommons.org/licenses/by-sa/3.0/us/>).
projects / catagits/Catalyst-Manual.git / blobdiff