Attention
This manual is no longer being maintained for TYPO3 versions 11.5 and above. The majority of the content has been migrated to the Extbase or Fluid sections in "TYPO3 Explained".
Using boolean conditions¶
Boolean conditions are queries that compare two
values with each other (e.g. with ==
or >=
) and
then returns the value true
or false
. Which values
are interpreted as true
or false
by Fluid depends
on the data type. A number for example is evaluated as true
if
it is greater than 0.
Tip
You find a complete list of all evaluating possibilities in appendix C in the section "Boolean expressions".
With the help of conditions you can hide or show certain parts of a
template. A typical scenario is the display of search results: If search
results are found, they were displayed; if none results are found an
appropriate message should be displayed. In Fluid the
IfViewHelper
enables such case-by-case analysis.
Simple if
queries (without an else term) looks like
this:
<f:if condition="{blog.posts}">
This is only shown if blog posts are available.
</f:if>
Tip
If none comparison operator like ==
is given, per
default empty lists are interpreted as false
and list with at
least one element as true
.
Using the inline notation it looks like this:
<div class="{f:if(condition: blog.posts, then: 'blogPostsAvailable')}">
This div has the CSS class 'BlogPostAvailable', if blog posts are available.
</div>
Also if-then-else
structures are possible. In that case
the then
tag is required:
<f:if condition="{blog.posts}">
<f:then>
This is only shown if blog posts are available.
</f:then>
<f:else>
No blog posts available.
</f:else>
</f:if>
This is also possible in the inline notation:
<div class="{f:if(condition: blog.posts, then: 'blogPostsAvailable', else: 'noPosts')}">
This div has the CSS class 'BlogPostAvailable', if blog posts are available.
If no posts are available this div container gets the CSS class 'noPosts' assigned.
</div>
Realize complex comparisons¶
Until now we have employed with simplest boolean evaluations. With the syntax you have learned until now, no comparisons or modulo operations are possible. Fluid supports these conditions as well. Here is a short example:
<f:if condition="{posts.viewCount} % 2">
viewCount is an even number.
</f:if>
Note the enhanced syntax inside the condition.
The compare operators >
, >=
,
<
, <=
, ==
, !=
and %
are available. The parameter left and right of the
operators could be numbers, object accessors, arrays and ViewHelpers in
inline notation, or quoted strings.
Tip
Any ViewHelper argument declared as boolean
supports boolean
expression syntax, including in your own self-written ViewHelpers.