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CGI::FormBuilder::Template - template adapters for FormBuilder

NAME
SYNOPSIS
DESCRIPTION

HTML::Template
Template Toolkit
Text::Template

SUBCLASSING
SEE ALSO
REVISION
AUTHOR

NAME

CGI::FormBuilder::Template - template adapters for FormBuilder

SYNOPSIS

    # Define a template engine

    package CGI::FormBuilder::Template::Type;

    sub render {
        my $form = shift;   # first arg is form object
        my %args = @_;      # remaining args are 'template' opts

        # ... code ...

        return $html;       # scalar HTML is returned
    }

DESCRIPTION

This documentation describes the usage of FormBuilder templates, as well as how to write your own template adapter.

The template engines serve as adapters between CPAN template modules and FormBuilder. A template engine is invoked by using the template option to the top-level new() method:

    my $form = CGI::FormBuilder->new(
                    template => 'filename.tmpl'
               );

This example points to a filename that contains an HTML::Template compatible template to use to layout the HTML. You can also specify the template option as a reference to a hash, allowing you to further customize the template processing options, or use other template engines.

For example, you could turn on caching in HTML::Template with something like the following:

    my $form = CGI::FormBuilder->new(
                    fields => \@fields,
                    template => {
                        filename => 'form.tmpl',
                        shared_cache => 1
                    }
               );

As mentioned, specifying a hashref allows you to use an alternate template processing system like the Template Toolkit. A minimal configuration would look like this:

    my $form = CGI::FormBuilder->new(
                    fields => \@fields,
                    template => {
                        type => 'TT2',      # use Template Toolkit
                        template => 'form.tmpl',
                    },
               );

The type option specifies the name of the engine. Currently accepted types are:

    HTML  -   HTML::Template (default)
    Text  -   Text::Template
    TT2   -   Template Toolkit

All other options besides type are passed to the constructor for that templating system verbatim, so you'll need to consult those docs to see what all the different options do.

Let's look at each template solution in turn.

HTML::Template

HTML::Template is the default template option and is activated one of two ways. Either:

    my $form = CGI::FormBuilder->new(
                    fields => \@fields,
                    template => $filename
               );

Or, you can specify any options which HTML::Template->new accepts by using a hashref:

    my $form = CGI::FormBuilder->new(
                    fields => \@fields,
                    template => {
                        filename => $filename,
                        die_on_bad_params => 0,
                        shared_cache => 1,
                        loop_context_vars => 1
                    }
                );

In your template, each of the form fields will correspond directly to a <tmpl_var> of the same name prefixed with ``field-'' in the template. So, if you defined a field called ``email'', then you would setup a variable called <tmpl_var field-email> in your template, and this would be expanded to the complete HTML <input> tag.

In addition, there are a couple special fields:

    <tmpl_var js-head>     -  JavaScript to stick in <head>
    <tmpl_var form-title>  -  The <title> of the HTML form
    <tmpl_var form-start>  -  Opening <form> tag and internal fields
    <tmpl_var form-submit> -  The submit button(s)
    <tmpl_var form-reset>  -  The reset button
    <tmpl_var form-end>    -  Just the closing </form> tag

Let's look at an example userinfo.tmpl template we could use:

    <html>
    <head>
    <title>User Information</title>
    <tmpl_var js-head><!-- this holds the JavaScript code -->
    </head>
    <tmpl_var form-start><!-- this holds the initial form tag -->
    <h3>User Information</h3>
    Please fill out the following information:
    <!-- each of these tmpl_var's corresponds to a field -->
    <p>Your full name: <tmpl_var field-name>
    <p>Your email address: <tmpl_var field-email>
    <p>Choose a password: <tmpl_var field-password>
    <p>Please confirm it: <tmpl_var field-confirm_password>
    <p>Your home zipcode: <tmpl_var field-zipcode>
    <p>
    <tmpl_var form-submit><!-- this holds the form submit button -->
    </form><!-- can also use "tmpl_var form-end", same thing -->

As you see, you get a <tmpl_var> for each for field you define.

However, you may want even more control. That is, maybe you want to specify every nitty-gritty detail of your input fields, and just want this module to take care of the statefulness of the values. This is no problem, since this module also provides several other <tmpl_var> tags as well:

    <tmpl_var value-[field]>   - The value of a given field
    <tmpl_var label-[field]>   - The human-readable label
    <tmpl_var comment-[field]> - Any optional comment
    <tmpl_var error-[field]>   - Error text if validation fails

This means you could say something like this in your template:

    <tmpl_var label-email>:
    <input type="text" name="email" value="<tmpl_var value-email>">
    <font size="-1"><i><tmpl_var error-email></i></font>

And FormBuilder would take care of the value stickiness for you, while you have control over the specifics of the <input> tag. A sample expansion may create HTML like the following:

    Email:
    <input type="text" name="email" value="nate@wiger">
    <font size="-1"><i>You must enter a valid value</i></font>

Note, though, that this will only get the first value in the case of a multi-value parameter (for example, a multi-select list). To remedy this, if there are multiple values you will also get a <tmpl_var> prefixed with ``loop-''. So, if you had:

    myapp.cgi?color=gray&color=red&color=blue

This would give the color field three values. To create a select list, you would do this in your template:

    <select name="color" multiple>
    <tmpl_loop loop-color>
        <option value="<tmpl_var value>"><tmpl_var label></option>
    </tmpl_loop>
    </select>

With <tmpl_loop> tags, each iteration gives you several variables:

    Inside <tmpl_loop>, this...  Gives you this
    ---------------------------  -------------------------------
    <tmpl_var value>             value of that option
    <tmpl_var label>             label for that option
    <tmpl_var checked>           if selected, the word "checked"
    <tmpl_var selected>          if selected, the word "selected"

Please note that <tmpl_var value> gives you one of the options, not the values. Why? Well, if you think about it you'll realize that select lists and radio groups are fundamentally different from input boxes in a number of ways. Whereas in input tags you can just have an empty value, with lists you need to iterate through each option and then decide if it's selected or not.

When you need precise control in a template this is all exposed to you; normally FormBuilder does all this magic for you. If you don't need exact control over your lists, simply use the <tmpl_var field-[name]> tag and this will all be done automatically, which I strongly recommend.

But, let's assume you need exact control over your lists. Here's an example select list template:

    <select name="color" multiple>
    <tmpl_loop loop-color>
    <option value="<tmpl_var value>" <tmpl_var selected>><tmpl_var label>
    </tmpl_loop>
    </select>

Then, your Perl code would fiddle the field as follows:

    $form->field( 
              name => 'color', nameopts => 1,
              options => [qw(red green blue yellow black white gray)]
           );

Assuming query string as shown above, the template would then be expanded to something like this:

    <select name="color" multiple>
    <option value="red" selected>Red
    <option value="green" >Green
    <option value="blue" selected>Blue
    <option value="yellow" >Yellow
    <option value="black" >Black
    <option value="white" >White
    <option value="gray" selected>Gray
    </select>

Notice that the <tmpl_var selected> tag is expanded to the word ``selected'' when a given option is present as a value as well (i.e., via the CGI query). The <tmpl_var value> tag expands to each option in turn, and <tmpl_var label> is expanded to the label for that value. In this case, since nameopts was specified to field(), the labels are automatically generated from the options.

Let's look at one last example. Here we want a radio group that allows a person to remove themself from a mailing list. Here's our template:

    Do you want to be on our mailing list?
    <p><table>
    <tmpl_loop loop-mailopt>
    <td bgcolor="silver">
      <input type="radio" name="mailopt" value="<tmpl_var value>">
    </td>
    <td bgcolor="white"><tmpl_var label></td>
    </tmpl_loop>
    </table>

Then, we would twiddle our mailopt field via field():

    $form->field(
              name => 'mailopt',
              options => [
                 [ 1 => 'Yes, please keep me on it!' ],
                 [ 0 => 'No, remove me immediately.' ]
              ]
           );

When the template is rendered, the result would be something like this:

    Do you want to be on our mailing list?
    <p><table>

    <td bgcolor="silver">
      <input type="radio" name="mailopt" value="1">
    </td>
    <td bgcolor="white">Yes, please keep me on it!</td>

    <td bgcolor="silver">
      <input type="radio" name="mailopt" value="0">
    </td>
    <td bgcolor="white">No, remove me immediately</td>

    </table>

When the form was then sumbmitted, you would access the values just like any other field:

    if ($form->field('mailopt')) {
        # is 1, so add them
    } else {
        # is 0, remove them
    }

Finally, you can also loop through each of the fields using the top-level fields loop in your template. This allows you to reuse the same template even if your parameters change. The following template code would loop through each field, creating a table row for each:

    <table>
    <tmpl_loop fields>
    <tr>
    <td class="small"><tmpl_var label></td>
    <td><tmpl_var field></td>
    </tr>
    </tmpl_loop>
    </table>

Each loop will have a label, field, value, etc, just like above.

For more information on templates, see the HTML::Template manpage.

Template Toolkit

Thanks to a huge patch from Andy Wardley, FormBuilder also supports Template Toolkit. Recall the first example way back at the top where we introduced HTML::Template. You can also do a similar thing using the Template Toolkit (http://template-toolkit.org/) to generate the form. This time, specify the template option as a hashref which includes the type option set to TT2 and the template option to denote the name of the template you want processed. You can also add variable as an option (among others) to denote the variable name that you want the form data to be referenced by.

    my $form = CGI::FormBuilder->new(
                    fields => \@fields,
                    template => {
                        type => 'TT2',
                        template => 'userinfo.tmpl',
                        variable => 'form',
                    }
               );

The template might look something like this:

    <html>
    <head>
      <title>[% form.title %]</title>
      [% form.jshead %]
    </head>
    <body>
      [% form.start %]
      <table>
        [% FOREACH field = form.fields %]
        <tr valign="top">
          <td>
            [% field.required
                  ? "<b>$field.label</b>"
                  : field.label
            %]
          </td>
          <td>
            [% IF field.invalid %]
            Missing or invalid entry, please try again.
        <br/>
        [% END %]

        [% field.field %]
      </td>
    </tr>
        [% END %]
        <tr>
          <td colspan="2" align="center">
            [% form.submit %] [% form.reset %]
          </td>
        </tr>
      </table>
      [% form.end %]
    </body>
    </html>

By default, the Template Toolkit makes all the form and field information accessible through simple variables.

    [% jshead %]  -  JavaScript to stick in <head>
    [% title  %]  -  The <title> of the HTML form
    [% start  %]  -  Opening <form> tag and internal fields
    [% submit %]  -  The submit button(s)
    [% reset  %]  -  The reset button
    [% end    %]  -  Closing </form> tag
    [% fields %]  -  List of fields
    [% field  %]  -  Hash of fields (for lookup by name)

You can specify the variable option to have all these variables accessible under a certain namespace. For example:

    my $form = CGI::FormBuilder->new(
        fields => \@fields,
        template => {
             type => 'TT2',
             template => 'form.tmpl',
             variable => 'form'
        },
    );

With variable set to form the variables are accessible as:

    [% form.jshead %]
    [% form.start  %]
    etc.

You can access individual fields via the field variable.

    For a field named...  The field data is in...
    --------------------  -----------------------
    job                   [% form.field.job   %]
    size                  [% form.field.size  %]
    email                 [% form.field.email %]

Each field contains various elements. For example:

    [% myfield = form.field.email %]

    [% myfield.label    %]  # text label
    [% myfield.field    %]  # field input tag
    [% myfield.value    %]  # first value
    [% myfield.values   %]  # list of all values
    [% myfield.option   %]  # first value
    [% myfield.options  %]  # list of all values
    [% myfield.required %]  # required flag
    [% myfield.invalid  %]  # invalid flag

The fields variable contains a list of all the fields in the form. To iterate through all the fields in order, you could do something like this:

    [% FOREACH field = form.fields %]
    <tr>
     <td>[% field.label %]</td> <td>[% field.field %]</td>
    </tr>
    [% END %]

If you want to customise any of the Template Toolkit options, you can set the engine option to contain a reference to an existing Template object or hash reference of options which are passed to the Template constructor. You can also set the data item to define any additional variables you want accesible when the template is processed.

    my $form = CGI::FormBuilder->new(
        fields => \@fields,
        template => {
             type => 'TT2',
             template => 'form.tmpl',
             variable => 'form'
             engine   => {
                  INCLUDE_PATH => '/usr/local/tt2/templates',
             },
             data => {
                  version => 1.23,
                  author  => 'Fred Smith',
             },
        },
    );

For further details on using the Template Toolkit, see Template or www.template-toolkit.org

Text::Template

Also thanks to a user contribution, this time by Jonathan Buhacoff, Text::Template is also supported. Usage is very similar to Template Toolkit:

    my $form = CGI::FormBuilder->new(
                    fields => \@fields,
                    template => {
                        type => 'Text',           # use Text::Template
                        template => 'form.tmpl',
                    }
               );

The default options passed into Text::Template-new()> with this calling form are:

    TYPE   => 'FILE'
    SOURCE => 'form.tmpl'
    DELIMITERS => ['<%','%>']

As these params are passed for you, your template will look very similar to ones used by Template Toolkit and HTML::Mason (the Text::Template default delimiters are { and }, but using alternative delimiters speeds it up by about 25%, and the <% and %> delimiters are good, familiar-looking alternatives).

    <% $jshead %>  -  JavaScript to stick in <head>
    <% $title  %>  -  The <title> of the HTML form
    <% $start  %>  -  Opening <form> tag and internal fields
    <% $submit %>  -  The submit button(s)
    <% $reset  %>  -  The reset button
    <% $end    %>  -  Closing </form> tag
    <% $fields %>  -  List of fields
    <% $field  %>  -  Hash of fields (for lookup by name)

Note that you refer to variables with a preceding $, just like in Perl. Like Template Toolkit, you can specify a variable to place fields under:

    my $form = CGI::FormBuilder->new(
        fields => \@fields,
        template => {
             type => 'Text',
             template => 'form.tmpl',
             variable => 'form'
        },
    );

Unlike Template Toolkit, though, these will not be placed in OO-style, dot-separated vars. Instead, a hash will be created which you then reference:

    <% $form{jshead} %>
    <% $form{start}  %>
    etc.

And field data is in a hash-of-hashrefs format:

    For a field named...  The field data is in...
    --------------------  -----------------------
    job                   <% $form{field}{job}   %]
    size                  <% $form{field}{size}  %]
    email                 <% $form{field}{email} %]

Since Text::Template looks so much like Perl, you can access individual elements and create variables like so:

    <%
        my $myfield = $form{field}{email};
        $myfield->{label};  # text label
        $myfield->{field}; # field input tag
        $myfield->{value}; # first value
        $myfield->{values}; # list of all values
        $myfield->{option}; # first option
        $myfield->{options}; # list of all options
        $myfield->{required}; # required flag
        $myfield->{invalid}; # invalid flag
    %>

    <%
        for my $field (@{$form{fields}}) {
            $OUT .= "<tr>\n<td>" . $field->{label} . "</td> <td>" . $field->{field} . "</td>\n<tr>";
        }
    %>

In addition, when using the engine option, as in Template Toolkit, you can supply an existing Text::Template object or a hash of parameters to be passed to new(). For example, you can ask for different delimiters yourself:

    my $form = CGI::FormBuilder->new(
        fields => \@fields,
        template => {
             type => 'Text',
             template => 'form.tmpl',
             variable => 'form',
             engine   => {
                DELIMITERS => [ '[@--', '--@]' ],
             },
             data => {
                  version => 1.23,
                  author  => 'Fred Smith',
             },
        },
    );

If you pass a hash of parameters, you can override the TYPE and SOURCE parameters, as well as any other Text::Template options. For example, you can pass in a string template with TYPE => STRING instead of loading it from a file. You must specify both TYPE and SOURCE if doing so. The good news is this is trivial:

    my $form = CGI::FormBuilder->new(
        fields => \@fields,
        template => {
             type => 'Text',
             variable => 'form',
             engine   => {
                  TYPE => 'STRING',
                  SOURCE => $string,
                  DELIMITERS => [ '[@--', '--@]' ],
             },
             data => {
                  version => 1.23,
                  author  => 'Fred Smith',
             },
        },
    );

If you get the crazy idea to let users of your application pick the template file (strongly discouraged) and you're getting errors, look at the Text::Template documentation for the UNTAINT feature.

Also, note that Text::Template's PREPEND => 'use strict;' option is not recommended due to the dynamic nature for FormBuilder. If you use it, then you'll have to declare each variable that FormBuilder puts into your template with use vars qw($jshead' ... etc);

If you're really stuck on this, though, a workaround is to say:

    PREPEND => 'use strict; use vars qw(%form);'

and then set the option variable => 'form'. That way you can have strict Perl without too much hassle, except that your code might be exhausting to look at :-). Things like $form{field}{your_field_name}{field} end up being all over the place, instead of the nicer short forms.

Finally, when you use the data template option, the keys you specify will be available to the template as regular variables. In the above example, these would be <% $version %> and <% $author %>. And complex datatypes are easy:

    data => {
            anArray => [ 1, 2, 3 ],
            aHash => { orange => 'tangy', chocolate => 'sweet' },
    }

This becomes the following in your template:

    <%
        @anArray;    # you can use $myArray[1] etc.
        %aHash;      # you can use $myHash{chocolate} etc.
    %>

For more information, please consult the Text::Template documentation.

SUBCLASSING

In addition to the above included template engines, it is also possible to write your own rendering module. If you come up with something cool, please let the mailing list know!

To do so, you need to write a module which has a sub called render(). This sub will be called by FormBuilder when $form->render is called. This sub can do basically whatever it wants, the only thing it has to do is return a scalar string which is the HTML to print out. The best thing to do is look through the guys of one of the existing template engines and go from there.

REVISION

$Id: Template.pm,v 1.7 2005/02/10 20:15:52 nwiger Exp $

AUTHOR

This module is free software; you may copy this under the terms of the GNU General Public License, or the Artistic License, copies of which should have accompanied your Perl kit.