Call ViewHelper from outside Fluid template - typo3

Question

In my general page setup, I define the template as follows: page.10.template.file = fileadmin/template.html
Is there a way to call a MVC ViewHelper in this template? The snippet
{namespace xyz=PATH\TO\MY\ViewHelpers}
<xyz:myhelper argument="abc" />
does not work in the above template, it is surfaced as is.

Answer 1

It is not 100% clear for me, which cObject you use for your page template. If you would like to use Fluid ViewHelpers in your page template, then I would recommend to use FLUIDTEMPLATE for your page template.
1. FLUIDTEMPLATE
If you use FLUIDTEMPLATE for your page template, then you can use any available ViewHelper (from FLUID or any other ExtBase/Fluid extension) directly in your template (see example below).
TypoScript
page = PAGE
page.10 = FLUIDTEMPLATE
page.10 {
template = FILE
template.file = fileadmin/templates/template.html
partialRootPath = fileadmin/templates/Partials/
layoutRootPath = fileadmin/templates/Layouts/
variables {
content < styles.content.get
content.select.where = colPos=1
}
}
Content of file: fileadmin/templates/template.html
{namespace xyz=NAMESPACE\EXTENSION\ViewHelpers}
<f:layout name="Main" />
<f:section name="Content">
<xyz:myhelper argument="abc" />
<f:format.html parseFuncTSPath="">{content}</f:format.html>
</f:section>
Content of file: fileadmin/templates/Layouts/Main.html
<f:render section="Content" />
2. TEMPLATE
If you use TEMPLATE (with markers and subparts), then you can't directly use Fluid ViewHelpers in that template. But you could define a marker which renders the FLUID ViewHelper like shown below.
TypoScript
page = PAGE
page.10 = TEMPLATE
page.10 {
template = FILE
template.file = fileadmin/templates/template.html
marks {
CONTENT < styles.content.get
VIEWHELPER = FLUIDTEMPLATE
VIEWHELPER {
template = FILE
template.file = fileadmin/templates/viewhelper.html
partialRootPath = fileadmin/templates/Partials/
layoutRootPath = fileadmin/templates/Layouts/
}
}
workOnSubpart = DOCUMENT
}
Content of file: fileadmin/templates/template.html
<!--###DOCUMENT### Start-->
###VIEWHELPER###
###CONTENT###
<!--###DOCUMENT### end-->
Content of file: fileadmin/templates/viewhelper.html
{namespace xyz=NAMESPACE\EXTENSION\ViewHelpers}
<f:layout name="Main" />
<f:section name="Content">
<xyz:myhelper argument="abc" />
</f:section>
Content of file: fileadmin/templates/Layouts/Main.html
<f:render section="Content" />