Remove now old mention of "used more than once" errors

[catagits/Catalyst-Manual.git] / lib / Catalyst / Manual / Tutorial / 09_AdvancedCRUD / 09_FormFu.pod

=head1 NAME

Catalyst::Manual::Tutorial::09_AdvancedCRUD::09_FormFu - Catalyst Tutorial - Chapter 9: Advanced CRUD - FormFu


=head1 OVERVIEW

This is B<Chapter 9 of 10> for the Catalyst tutorial.

L<Tutorial Overview|Catalyst::Manual::Tutorial>

=over 4

=item 1

L<Introduction|Catalyst::Manual::Tutorial::01_Intro>

=item 2

L<Catalyst Basics|Catalyst::Manual::Tutorial::02_CatalystBasics>

=item 3

L<More Catalyst Basics|Catalyst::Manual::Tutorial::03_MoreCatalystBasics>

=item 4

L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>

=item 5

L<Authentication|Catalyst::Manual::Tutorial::05_Authentication>

=item 6

L<Authorization|Catalyst::Manual::Tutorial::06_Authorization>

=item 7

L<Debugging|Catalyst::Manual::Tutorial::07_Debugging>

=item 8

L<Testing|Catalyst::Manual::Tutorial::08_Testing>

=item 9

B<09_Advanced CRUD::09_FormFu>

=item 10

L<Appendices|Catalyst::Manual::Tutorial::10_Appendices>

=back


=head1 DESCRIPTION

This portion of the tutorial explores L<HTML::FormFu|HTML::FormFu> and 
how it can be used to manage forms, perform validation of form input, 
as well as save and restore data to/from the database.  This was written
using HTML::FormFu version 0.05001.

See 
L<Catalyst::Manual::Tutorial::09_AdvancedCRUD|Catalyst::Manual::Tutorial::09_AdvancedCRUD>
for additional form management options other than 
L<HTML::FormFu|HTML::FormFu>.


=head1 HTML::FormFu FORM CREATION

This section looks at how L<HTML::FormFu|HTML::FormFu> can be used to 
add additional functionality to the manually created form from Chapter 4.


=head2 Inherit From Catalyst::Controller::HTML::FormFu

First, change your C<lib/MyApp/Controller/Books.pm> to inherit from
L<Catalyst::Controller::HTML::FormFu|Catalyst::Controller::HTML::FormFu>
by changing the C<extends> line from the default of:

    BEGIN {extends 'Catalyst::Controller'; }

to use the FormFu base controller class:

    BEGIN {extends 'Catalyst::Controller::HTML::FormFu'; }

Don't forget to add:

    requires 'Catalyst::Controller::HTML::FormFu';

to your C<Makefile.PL>.

=head2 Add Action to Display and Save the Form

Open C<lib/MyApp/Controller/Books.pm> in your editor and add the
following method:

    =head2 formfu_create
    
    Use HTML::FormFu to create a new book
    
    =cut
    
    sub formfu_create :Chained('base') :PathPart('formfu_create') :Args(0) :FormConfig {
        my ($self, $c) = @_;
    
        # Get the form that the :FormConfig attribute saved in the stash
        my $form = $c->stash->{form};
  
        # Check if the form has been submitted (vs. displaying the initial
        # form) and if the data passed validation.  "submitted_and_valid"
        # is shorthand for "$form->submitted && !$form->has_errors"
        if ($form->submitted_and_valid) {
            # Create a new book
            my $book = $c->model('DB::Book')->new_result({});
            # Save the form data for the book
            $form->model->update($book);
            # Set a status message for the user
            $c->flash->{status_msg} = 'Book created';
            # Return to the books list
            $c->response->redirect($c->uri_for($self->action_for('list'))); 
            $c->detach;
        } else {
            # Get the authors from the DB
            my @author_objs = $c->model("DB::Author")->all();
            # Create an array of arrayrefs where each arrayref is an author
            my @authors;
            foreach (sort {$a->last_name cmp $b->last_name} @author_objs) {
                push(@authors, [$_->id, $_->last_name]);
            }
            # Get the select added by the config file
            my $select = $form->get_element({type => 'Select'});
            # Add the authors to it
            $select->options(\@authors);
        }
        
        # Set the template
        $c->stash->{template} = 'books/formfu_create.tt2';
    }


=head2 Create a Form Config File

Although C<HTML::FormFu> supports any configuration file handled by
L<Config::Any|Config::Any>, most people tend to use YAML.  First
create a directory to hold your form configuration files:

    mkdir -p root/forms/books

Then create the file C<root/forms/books/formfu_create.yml> and enter the 
following text:

    ---
    # indicator is the field that is used to test for form submission
    indicator: submit
    # Start listing the form elements
    elements:
        # The first element will be a text field for the title
        - type: Text
          name: title
          label: Title
          # This is an optional 'mouse over' title pop-up
          attributes:
            title: Enter a book title here
    
        # Another text field for the numeric rating
        - type: Text
          name: rating
          label: Rating
          attributes:
            title: Enter a rating between 1 and 5 here
    
        # Add a drop-down list for the author selection.  Note that we will
        # dynamically fill in all the authors from the controller but we
        # could manually set items in the drop-list by adding this YAML code:
        # options:
        #   - [ '1', 'Bastien' ]
        #   - [ '2', 'Nasseh'  ]
        - type: Select
          name: authors
          label: Author
    
        # The submit button
        - type: Submit
          name: submit
          value: Submit

B<NOTE:> Copying and pasting YAML from perl documentation is sometimes
tricky.  See the L<Config::General Config for this tutorial> section of
this document for a more foolproof config format.


=head2 Update the CSS

Edit C<root/static/css/main.css> and add the following lines to the bottom of
the file:

    ...
    input {
        display: block;
    }
    select {
        display: block;
    }
    .submit {
        padding-top: .5em;
        display: block;
    }

These changes will display form elements vertically.  Note that the 
existing definition of the C<.error> class is pulling the color scheme 
settings from the C<root/lib/config/col> file that was created by the 
TTSite helper.  This allows control over the CSS color settings from a 
single location.


=head2 Create a Template Page To Display The Form

Open C<root/src/books/formfu_create.tt2> in your editor and enter the following:

    [% META title = 'Create/Update Book' %]
    
    [%# Render the HTML::FormFu Form %]
    [% form %]
    
    <p><a href="[% c.uri_for(c.controller.action_for('list')) %]">Return to book list</a></p>


=head2 Add Links for Create and Update via C<HTML::FormFu>

Open C<root/src/books/list.tt2> in your editor and add the following to
the bottom of the existing file:

    ...
    <p>
      HTML::FormFu:
      <a href="[% c.uri_for(c.controller.action_for('formfu_create')) %]">Create</a>
    </p>

This adds a new link to the bottom of the book list page that we can
use to easily launch our HTML::FormFu-based form.


=head2 Test The HTML::FormFu Create Form

Press C<Ctrl-C> to kill the previous server instance (if it's still
running) and restart it:

    $ script/myapp_server.pl

Login as C<test01> (password: mypass).  Once at the Book List page,
click the new HTML::FormFu "Create" link at the bottom to display the
form.  Fill in the following values:

Title:  Internetworking with TCP/IP Vol. II
Rating: 4
Author: Comer
    
Click the Submit button, and you will be returned to the Book List page
with a "Book created" status message displayed.

Also note that this implementation allows you to create books with any
bogus information.  Although we have constrained the authors with the 
drop-down list (note that this isn't bulletproof because we still have 
not prevented a user from "hacking" the form to specify other values), 
there are no restrictions on items such as the length of the title (for 
example, you can create a one-letter title) and the value of the rating 
(you can use any number you want, and even non-numeric values with 
SQLite).  The next section will address this concern.

B<Note:> Depending on the database you are using and how you established
the columns in your tables, the database could obviously provide various
levels of "type enforcement" on your data.  The key point being made in
the previous paragraph is that the I<web application> itself is not
performing any validation.


=head1 HTML::FormFu VALIDATION AND FILTERING

Although the use of L<HTML::FormFu|HTML::FormFu> in the previous section 
did provide an automated mechanism to build the form, the real power of 
this module stems from functionality that can automatically validate and 
filter the user input.  Validation uses constraints to be sure that 
users input appropriate data (for example, that the email field of a 
form contains a valid email address).  Filtering can also be used to 
remove extraneous whitespace from fields or to escape meta-characters in 
user input.


=head2 Add Constraints

Open C<root/forms/books/formfu_create.yml> in your editor and update it 
to match:

    ---
    # indicator is the field that is used to test for form submission
    indicator: submit
    # Start listing the form elements
    elements:
        # The first element will be a text field for the title
        - type: Text
          name: title
          label: Title
          # This is an optional 'mouse over' title pop-up
          attributes:
            title: Enter a book title here
          # Add constraints for the field
          constraints:
            # Force the length to be between 5 and 40 chars
            - type: Length
              min: 5
              max: 40
              # Override the default of 'Invalid input'
              message: Length must be between 5 and 40 characters
    
        # Another text field for the numeric rating
        - type: Text
          name: rating
          label: Rating
          attributes:
            title: Enter a rating between 1 and 5 here
          # Use Filter to clean up the input data
          # Could use 'NonNumeric' below, but since Filters apply *before*
          # constraints, it would conflict with the 'Integer' constraint below.
          # So let's skip this and just use the constraint.
          #filter:
            # Remove everything except digits
            #- NonNumeric
          # Add constraints to the field
          constraints:
            # Make sure it's a number
            - type: Integer
              message: "Required. Digits only, please."
            # Check the min & max values
            - type: Range
              min: 1
              max: 5
              message: "Must be between 1 and 5."
    
        # Add a select list for the author selection.  Note that we will
        # dynamically fill in all the authors from the controller but we
        # could manually set items in the select by adding this YAML code:
        # options:
        #   - [ '1', 'Bastien' ]
        #   - [ '2', 'Nasseh'  ]
        - type: Select
          name: authors
          label: Author
          # Convert the drop-down to a multi-select list
          multiple: 1
          # Display 3 entries (user can scroll to see others)
          size: 3
          # One could argue we don't need to do filters or constraints for
          # a select list, but it's smart to do validation and sanity
          # checks on this data in case a user "hacks" the input
          # Add constraints to the field
          constraints:
            # Make sure it's a number
            - Integer
    
        # The submit button
        - type: Submit
          name: submit
          value: Submit
    
    # Global filters and constraints.
    constraints:
      # The user cannot leave any fields blank
      - Required
      # If not all fields are required, move the Required constraint to the 
      # fields that are
    filter:
      # Remove whitespace at both ends
      - TrimEdges
      # Escape HTML characters for safety
      - HTMLEscape

B<NOTE:> Copying and pasting YAML from perl documentation is sometimes
tricky.  See the L<Config::General Config for this tutorial> section of
this document for a more foolproof config format.

The main changes are:

=over 4

=item *

The C<Select> element for C<authors> is changed from a single-select
drop-down to a multi-select list by adding configuration for the 
C<multiple> and C<size> options in C<formfu_create.yml>.

=item *

Constraints are added to provide validation of the user input.  See
L<HTML::FormFu::Constraint|HTML::FormFu::Constraint> for other
constraints that are available.

=item *

A variety of filters are run on every field to remove and escape 
unwanted input.  See L<HTML::FormFu::Filter|HTML::FormFu::Filter>
for more filter options.

=back


=head2 Try Out the Updated Form

Press C<Ctrl-C> to kill the previous server instance (if it's still 
running) and restart it:

    $ script/myapp_server.pl

Make sure you are still logged in as C<test01> and try adding a book 
with various errors: title less than 5 characters, non-numeric rating, a 
rating of 0 or 6, etc.  Also try selecting one, two, and zero authors. 
When you click Submit, the HTML::FormFu C<constraint> items will 
validate the logic and insert feedback as appropriate.  Try adding blank 
spaces at the front or the back of the title and note that it will be 
removed.


=head1 CREATE AND UPDATE/EDIT ACTION

Let's expand the work done above to add an edit action.  First, open 
C<lib/MyApp/Controller/Books.pm> and add the following method to the 
bottom:

    =head2 formfu_edit
    
    Use HTML::FormFu to update an existing book
    
    =cut
    
    sub formfu_edit :Chained('object') :PathPart('formfu_edit') :Args(0) 
            :FormConfig('books/formfu_create.yml') {
        my ($self, $c) = @_;
    
        # Get the specified book already saved by the 'object' method
        my $book = $c->stash->{object};
    
        # Make sure we were able to get a book
        unless ($book) {
            $c->flash->{error_msg} = "Invalid book -- Cannot edit";
            $c->response->redirect($c->uri_for($self->action_for('list')));
            $c->detach;
        }
    
        # Get the form that the :FormConfig attribute saved in the stash
        my $form = $c->stash->{form};
    
        # Check if the form has been submitted (vs. displaying the initial
        # form) and if the data passed validation.  "submitted_and_valid"
        # is shorthand for "$form->submitted && !$form->has_errors"
        if ($form->submitted_and_valid) {
            # Save the form data for the book
            $form->model->update($book);
            # Set a status message for the user
            $c->flash->{status_msg} = 'Book edited';
            # Return to the books list
            $c->response->redirect($c->uri_for($self->action_for('list')));
            $c->detach;
        } else {
            # Get the authors from the DB
            my @author_objs = $c->model("DB::Author")->all();
            # Create an array of arrayrefs where each arrayref is an author
            my @authors;
            foreach (sort {$a->last_name cmp $b->last_name} @author_objs) {
                push(@authors, [$_->id, $_->last_name]);
            }
            # Get the select added by the config file
            my $select = $form->get_element({type => 'Select'});
            # Add the authors to it
            $select->options(\@authors);
            # Populate the form with existing values from DB
            $form->model->default_values($book);
        }
    
        # Set the template
        $c->stash->{template} = 'books/formfu_create.tt2';
    }

Most of this code should look familiar to what we used in the 
C<formfu_create> method (in fact, we should probably centralize some of 
the common code in separate methods).  The main differences are:

=over 4

=item *

We have to manually specify the name of the FormFu .yml file as an 
argument to C<:FormConfig> because the name can no longer be 
automatically deduced from the name of our action/method (by default,
FormFu would look for a file named C<books/formfu_edit.yml>).

=item *

We load the book object from the stash (found using the $id passed to 
the Chained object method)

=item *

We use C<$id> to look up the existing book from the database.

=item *

We make sure the book lookup returned a valid book.  If not, we set 
the error message and return to the book list.

=item *

If the form has been submitted and passes validation, we skip creating a 
new book and just use C<$form-E<gt>model-E<gt>update> to update the existing 
book.

=item *

If the form is being displayed for the first time (or has failed 
validation and it being redisplayed), we use
 C<$form-E<gt>model-E<gt>default_values> to populate the form with data from the
database.

=back

Then, edit C<root/src/books/list.tt2> and add a new link below the 
existing "Delete" link that allows us to edit/update each existing book. 
The last E<lt>tdE<gt> cell in the book list table should look like the 
following:

    ...
    <td>
      [% # Add a link to delete a book %]
      <a href="[% c.uri_for(c.controller.action_for('delete'), [book.id]) %]">Delete</a>
      [% # Add a link to edit a book %]
      <a href="[% c.uri_for(c.controller.action_for('formfu_edit'), [book.id]) %]">Edit</a>
    </td>
    ...

B<Note:> Only add two lines (the "Add a link to edit a book" comment
and the href for C<formfu_edit>).  Make sure you add it below the
existing C<delete> link.


=head2 Try Out the Edit/Update Feature

Press C<Ctrl-C> to kill the previous server instance (if it's still 
running) and restart it:

    $ script/myapp_server.pl

Make sure you are still logged in as C<test01> and go to the 
L<http://localhost:3000/books/list> URL in your browser.  Click the 
"Edit" link next to "Internetworking with TCP/IP Vol. II", change the 
rating to a 3, the "II" at end of the title to the number "2", add 
Stevens as a co-author (control-click), and click Submit.  You will then 
be returned to the book list with a "Book edited" message at the top in 
green.  Experiment with other edits to various books.


=head2 More Things to Try

You are now armed with enough knowledge to be dangerous.  You can keep
tweaking the example application; some things you might want to do:

=over 4

=item *

Add an appropriate authorization check to the new Edit function.

=item *

Cleanup the List page so that the Login link only displays when the user
isn't logged in and the Logout link only displays when a user is logged
in.

=item *

Add a more sensible policy for when and how users and admins can do
things in the CRUD cycle.

=item *

Support the CRUD cycle for authors.

=back

Or you can proceed to write your own application, which is probably the
real reason you worked through this Tutorial in the first place.


=head2  Config::General Config for this tutorial

If you are having difficulty with YAML config above, please save the
below into the file C<formfu_create.conf> and delete the
C<formfu_create.yml> file.  The below is in
L<Config::General|Config::General> format which follows the syntax of
Apache config files.

   constraints   Required
   <elements>
       <constraints>
           min   5
           max   40
           type   Length
           message   Length must be between 5 and 40 characters
       </constraints>
       filter   TrimEdges
       filter   HTMLEscape
       name   title
       type   Text
       label   Title
       <attributes>
           title   Enter a book title here
       </attributes>
   </elements>
   <elements>
       constraints   Integer
       filter   TrimEdges
       filter   NonNumeric
       name   rating
       type   Text
       label   Rating
       <attributes>
           title   Enter a rating between 1 and 5 here
       </attributes>
   </elements>
   <elements>
       constraints   Integer
       filter   TrimEdges
       filter   HTMLEscape
       name   authors
       type   Select
       label   Author
       multiple   1
       size   3
   </elements>
   <elements>
       value   Submit
       name   submit
       type   Submit
   </elements>
   indicator   submit
   

=head1 AUTHOR

Kennedy Clark, C<hkclark@gmail.com>

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/Catalyst-Manual/5.80/trunk/lib/Catalyst/Manual/Tutorial/>.

Copyright 2006-2008, Kennedy Clark, under Creative Commons License
(L<http://creativecommons.org/licenses/by-sa/3.0/us/>).