Synopsis
Form 1:
<#list sequence as item>
Part repeated for each item
<#else>
Part executed when there are 0 items
</#list>
Where:
-
The
elsepart is optional, and is only supported since FreeMarker 2.3.23. -
sequence: Expressions evaluates to a sequence or collection of the items we want to iterate through -
item: Name of the loop variable (not an expression) -
The various "parts" between the tags can
contain arbitrary FTL (including nested
list-s)
Form 2 (since FreeMarker 2.3.23):
<#list sequence>
Part executed once if we have more than 0 items
<#items as item>
Part repeated for each item
</#items>
Part executed once if we have more than 0 items
<#else>
Part executed when there are 0 items
</#list>
Where: Same as the "Where" section of Form 1 above.
Description
Simplest form
Assuming users contains the
['Joe', 'Kate', 'Fred'] sequence:
<#list users as user>
<p>${user}
</#list><p>Joe <p>Kate <p>Fred
The list directive executes the code
between the list start-tag and
list end-tag (the body of
list from now on) for each value in the
sequence (or collection) specified as its first parameter. For
each such iteration the loop variable (user in
this example) will store the value of the current item.
The loop variable (user) only exists
inside the list body. Also, macros/functions
called from within the loop won't see it (as if it were a local
variable).
else directive
else inside list is
only supported since FreeMarker 2.3.23
The else directive is used if when there
are 0 items, you have to print something special instead of just
printing nothing:
<#list users as user>
<p>${user}
<#else>
<p>No users
</#list>This outputs the same as the earlier example, except when
users contains 0 items:
<p>No users
Note that the loop variable (user)
doesn't exist between the else tag and the
list end-tag, since that part is not part of
the loop.
else must be literally (means, in the
source code) inside the body of the list
directive. That is, you can't moved it out into a macro or
included template.
items directive
items exists since FreeMarker
2.3.23
The items directive is used if you have
to print (or do) something before the first list item, and after
the last list item, as far as there's at least 1 item. A typical
example:
<#list users>
<ul>
<#items as user>
<li>${user}</li>
</#items>
</ul>
</#list> <ul>
<li>Joe</li>
<li>Kate</li>
<li>Fred</li>
</ul>If there are 0 items, the above won't print anything, thus
you don't end up with an empty
<ul></ul>.
That is, when the list directive has no
as item parameter,
the body of its is executed exactly once if there's at least one
item, or not at all otherwise. It's the body of the mandatory
nested items directive that will be run for
each item, and hence it's also the items
directive that defines the loop variable with as
item, not
list.
A list directive with
items also can have an else
directive:
<#list users>
<ul>
<#items as user>
<li>${user}</li>
</#items>
</ul>
<#else>
<p>No users
</#list>Some further details:
-
The parser will check that a
listwithoutas itemparameter always has a nesteditemsdirective, and that anitemsdirective always has an enclosinglistwhich has noas itemparameter. This is checked when the template is parsed, not when the template is executed. Thus, these rules apply on the FTL source code itself, so you can't moveitemsout into a macro or included template. -
A
listcan have multipleitemsdirectives, but only one of them will be allowed to run (as far as you don't leave and re-enter the enclosinglistdirective); and further attempts to callitemswill cause error. So multipleitemscan be utilized on differentif-elsebranches for example, but not for iterating twice. -
itemsdirective can't have its own nestedelsedirective, only the enclosinglistcan have -
The loop variable (
user) only exists inside the body of theitemsdirective.
sep directive
sep exists since FreeMarker
2.3.23
sep is used when you have to display
something between each item (but not before the first item or
after the last item). For example:
<#list users as user>${user}<#sep>, </#list>Joe, Kate, Fred
Above, <#sep>, </#list> is a
shorthand for <#sep>,
</#sep></#list>; the sep
end-tag can be omitted if you would put it where the enclosing
directive is closed anyway. In the next example, you couldn't use
such abbreviation (HTML tags close nothing, as they are just raw
text to output for FreeMarker):
<#list users as user>
<div>
${user}<#sep>, </#sep>
</div>
</#list>As sep is just a convenient way of
writing <#if
item?has_next>...</#if>,
it can be used anywhere where there's a list or
items loop variable is available, and for
unlimited times. Also, it can have arbitrary FTL as nested
content.
The parser will check that sep is used
inside list ... as
item or an items directive, so you
can't move sep out from the repeated part into
a macro or included template.
break directive
You can exit the iteration at any point with the
break directive. For example:
<#list 1..10 as x>
${x}
<#if x == 3>
<#break>
</#if>
</#list>1 2 3
The break directives can be placed
anywhere inside list as far as it has
as item parameter,
otherwise it can be placed anywhere inside the
items directive. If the
break is inside items, it
will only exit from items, not from
list. In general, break will
only exit from the directive whose body is called for each item,
and can only be placed inside such directive. So for example can't
use break inside list's
else section, unless there's the
list is nested into another
break-able directive.
Just like else and
items, break must be
literally inside body of the directive to break out from, and
can't be moved out into a macro or included template.
Accessing iteration state
Starting from 2.3.23, loop variable built-ins is
the preferred way of accessing current state of the iteration. For
example, here we use the counter and
item_parity loop variable built-ins (see all of
them in the
Reference):
<#list users>
<table>
<#items as user>
<tr class="${user?item_parity}Row">
<td>${user?counter}
<td>${user}
</#items>
</table>
</#list> <table>
<tr class="oddRow">
<td>1
<td>Joe
<tr class="evenRow">
<td>2
<td>Kate
<tr class="oddRow">
<td>3
<td>Fred
</table>In 2.3.22 and earlier, there were two extra loop variables to retrieve the iteration state instead (and they still exist for backward compatibility):
-
item_index(deprecated byitem?index): The index (0-based number) of the current item in the loop. -
item_has_next(deprecated byitem?has_next): Boolean value that tells if the current item is the last in the sequence or not.
so in the above example, you could replace
${user?counter} with ${user_index +
1}.
Nesting loops into each other
Naturally, list or
items can contain further
list-s:
<#list 1..2 as i>
<#list 1..3 as j>
i = ${i}, j = ${j}
</#list>
</#list> i = 1, j = 1
i = 1, j = 2
i = 1, j = 3
i = 2, j = 1
i = 2, j = 2
i = 2, j = 3It's also allowed to use clashing loop variable names like:
<#list 1..2 as i>
Outer: ${i}
<#list 10..12 as i>
Inner: ${i}
</#list>
Outer again: ${i}
</#list> Outer: 1
Inner: 10
Inner: 11
Inner: 12
Outer again: 1
Outer: 2
Inner: 10
Inner: 11
Inner: 12
Outer again: 2Notes for Java programmers
If classic compatible mode
list accepts a scalar too and treats it as a
single-element sequence.
If you pass an collection that
wraps an java.util.Iterator to the
list, you can iterate over its elements only
once, since Iterators are by their nature
one-off objects. When you try to list a such collection variable
for the second time, an error will abort template
processing.