Looping Over Data Passed to a Template

The example above shows how to display a single variable. What if you need to display the elements contained within a list? First, let’s take a look at our Hello World handler again and see how we build a data structure that can be looped or iterated over.

sub some_mode {
    my $app = shift;
    my $input = $app->{query}->param('some\_form_parameter');
    my $plugin = plugin();
    my $param = {};

    my @people;
    push @people, { person => 'David Byrne' };
    push @people, { person => 'Harper Ford' };
    $param->{people} = \@people;

    my $tmpl = $plugin->load_tmpl('some_template.tmpl');
    return $app->build_page( $tmpl, $param );
}

As the example above shows, a loop in Movable Type is nothing more than an array of hash references, or of name/value pairs. To loop over this data structure and display its contents, use the following template code:

<mt:setvarblock name="page_title">This is a page title</mt:setvarblock>
<mt:include name="include/header.tmpl">
<mt:loop name="people">
    <p>Hello <mt:var name="person">!</p>
</mt:loop>
<mt:include name="include/footer.tmpl">

In the above example you will have noticed that we have added the <mt:loop> tag. This tag takes as input the name of an array that was passed into the template as a parameter. Within the loop you can display the value of the elements contained within the array just like you do any other variable.

Loop Meta-Variables

To assist you in customizing the display of data within your loop, Movable Type manages for you a set of variables for you that can be used inside of a <mt:loop> construct. These “meta-loop variables” are:

• __first__ - returns true if the current element is the first element in the list.
• __last__ - returns true if the current element is the last element in the list.
• __index__ - returns the current index of the list being looped over (starting at 0)
• __counter__ - returns the number of times the current loop has been iterated over thus far (starting at 1)
• __odd__ - returns true if the current index is an odd number (e.g. 1, 3, 5, etc.)
• __even__ - returns true if the current index is an even number (e.g. 2, 4, 6, etc.)

For example, let’s use some of the above meta loop variables to create a properly formatted HTML list:

<mt:setvarblock name="page_title">This is a page title</mt:setvarblock>
<mt:include name="include/header.tmpl">
<mt:loop name="people">
    <mt:if name="__first__"><ul></mt:if>
    <li class="<mt:if name="__odd__">odd<mt:else>even</mt:if>">
      <mt:var name="__counter__">. Hello <mt:var name="person">!
    </li>
    <mt:if name="__last__"></ul></mt:if>
</mt:loop>
<mt:include name="include/footer.tmpl">