3:07 p.m.
I just thought of a feature I have often needed in Facelets that perhaps we
can weave into the VDL. It would be nice to know if a named template has
been defined inside the master template. Consider the following example:
page.xhtml
<ui:composition template="/WEB-INF/template.xhtml" ...>
<ui:param name="title" value="VDL Template Page"/>
<ui:define name="content">
<h:outputText value="Hello World" />
</ui:define>
</ui:composition>
template.xhtml
<html ...>
<h:head>
<title>#{not empty title ? title : 'My Site'}</title>
</h:head>
<body>
<div id="container">
<ui:insert name="content"/> <- how do I know if it has
been
defined?
</div>
</body>
</html>
Since the <ui:param> creates a regular variable, I can check whether it is
empty or not. But I do not have a way to check if the named template
"content" has been defined. Of course, I can nest default content within the
<ui:insert>, which is used when the named template is not defined, but there
are cases when I simply need to know whether or not it is defined. Could we
come up with some way to check if it is defined?
-Dan
--
Dan Allen
Senior Software Engineer, Red Hat | Author of Seam in Action
http://mojavelinux.com
http://mojavelinux.com/seaminaction
http://in.relation.to/Bloggers/Dan
NOTE: While I make a strong effort to keep up with my email on a daily
basis, personal or other work matters can sometimes keep me away
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9:58 a.m.
Hey Dan -
I agree that this would be a useful feature. I can easily imagine cases
where template authors may want to selectively render some bit of
content depending on whether a particular named template has been
ui:define'd.
Actually, a similar case may come up with composite component facets,
depending on how <composite:insertFacet> is implemented. If inserted
facets remain parented to the component component, then we should be
able to use #{compositeComponent.facets.<facet name here>} to check for
the presence of a particular facet. However, if insertFacet relocates
the facet component, seems like this would get trickier.
Andy
Dan Allen wrote On 4/8/2009 4:07 PM ET:
I just thought of a feature I have often needed in Facelets that
perhaps we can weave into the VDL. It would be nice to know if a named
template has been defined inside the master template. Consider the
following example:
page.xhtml
<ui:composition template="/WEB-INF/template.xhtml" ...>
<ui:param name="title" value="VDL Template Page"/>
<ui:define name="content">
<h:outputText value="Hello World" />
</ui:define>
</ui:composition>
template.xhtml
<html ...>
<h:head>
<title>#{not empty title ? title : 'My Site'}</title>
</h:head>
<body>
<div id="container">
<ui:insert name="content"/> <- how do I know if it has
been defined?
</div>
</body>
</html>
Since the <ui:param> creates a regular variable, I can check whether
it is empty or not. But I do not have a way to check if the named
template "content" has been defined. Of course, I can nest default
content within the <ui:insert>, which is used when the named template
is not defined, but there are cases when I simply need to know whether
or not it is defined. Could we come up with some way to check if it is
defined?
-Dan
--
Dan Allen
Senior Software Engineer, Red Hat | Author of Seam in Action
http://mojavelinux.com
http://mojavelinux.com/seaminaction
http://in.relation.to/Bloggers/Dan
NOTE: While I make a strong effort to keep up with my email on a daily
basis, personal or other work matters can sometimes keep me away
from my email. If you contact me, but don't hear back for more than a
week,
it is very likely that I am excessively backlogged or the message was
caught in the spam filters. Please don't hesitate to resend a message if
you feel that it did not reach my attention.
2:16 p.m.
2009/4/8 Dan Allen <dan.j.allen(a)gmail.com>
I just thought of a feature I have often needed in Facelets that
perhaps we
can weave into the VDL. It would be nice to know if a named template has
been defined inside the master template. Consider the following example:
page.xhtml
<ui:composition template="/WEB-INF/template.xhtml" ...>
<ui:param name="title" value="VDL Template Page"/>
<ui:define name="content">
<h:outputText value="Hello World" />
</ui:define>
</ui:composition>
template.xhtml
<html ...>
<h:head>
<title>#{not empty title ? title : 'My Site'}</title>
Alternatively, you can do <ui:insert name="title">My
Site</ui:insert> if you
ui:define title in page.xhtml, although last time I checked, I don't believe
that default values were working for ui:insert in Mojarra.
</h:head>
<body>
<div id="container">
<ui:insert name="content"/> <- how do I know if it has
been
defined?
</div>
</body>
</html>
Since the <ui:param> creates a regular variable, I can check whether it is
empty or not. But I do not have a way to check if the named template
"content" has been defined. Of course, I can nest default content within the
<ui:insert>, which is used when the named template is not defined, but there
are cases when I simply need to know whether or not
it is defined. Could we come up with some way to check if it is defined?
With default values, you should be able to do this:
<ui:insert name="content"></ui:insert>
And nothing should be inserted if content is not defined. Again, I don't
know if that works in Mojarra.
However, that solution (if it works) isn't good enough because page authors
should be able to conditionally render any chunk of XHTML, instead of just
conditionally inserting with ui:insert. For example, the container div in
the example above might have padding and a border, so if it has no content,
you'll get a rectangle with a border, instead of nothing. Therefore, you
want the page author to be able to conditionally render the div based on
whether content has been defined.
david
-Dan
--
Dan Allen
Senior Software Engineer, Red Hat | Author of Seam in Action
http://mojavelinux.com
http://mojavelinux.com/seaminaction
http://in.relation.to/Bloggers/Dan
NOTE: While I make a strong effort to keep up with my email on a daily
basis, personal or other work matters can sometimes keep me away
from my email. If you contact me, but don't hear back for more than a week,
it is very likely that I am excessively backlogged or the message was
caught in the spam filters. Please don't hesitate to resend a message if
you feel that it did not reach my attention.
4:38 p.m.
On Mon, Apr 13, 2009 at 3:16 PM, David Geary <clarity.training(a)gmail.com>wrote:
2009/4/8 Dan Allen <dan.j.allen(a)gmail.com>
> I just thought of a feature I have often needed in Facelets that perhaps
> we can weave into the VDL. It would be nice to know if a named template has
> been defined inside the master template. Consider the following example:
>
> page.xhtml
> <ui:composition template="/WEB-INF/template.xhtml" ...>
> <ui:param name="title" value="VDL Template Page"/>
> <ui:define name="content">
> <h:outputText value="Hello World" />
> </ui:define>
> </ui:composition>
>
> template.xhtml
> <html ...>
> <h:head>
> <title>#{not empty title ? title : 'My Site'}</title>
Alternatively, you can do <ui:insert name="title">My
Site</ui:insert> if
you ui:define title in page.xhtml, although last time I checked, I don't
believe that default values were working for ui:insert in Mojarra.
Naturally. But the fallback fragment only partially solves the problem. It
doesn't help if you need to perform logic based on whether or not a template
is defined, or enforce that two or more templates are defined. The point is,
there are many cases when I have encountered a need to know whether it's
been defined or not, irregardless of whether a fallback kicks in.
However, that solution (if it works) isn't good enough because page authors
should be able to conditionally render any chunk of XHTML, instead of just
conditionally inserting with ui:insert. For example, the container div in
the example above might have padding and a border, so if it has no content,
you'll get a rectangle with a border, instead of nothing. Therefore, you
want the page author to be able to conditionally render the div based on
whether content has been defined.
Exactly. It's not always so simple.
-Dan
--
Dan Allen
Senior Software Engineer, Red Hat | Author of Seam in Action
http://mojavelinux.com
http://mojavelinux.com/seaminaction
http://in.relation.to/Bloggers/Dan
NOTE: While I make a strong effort to keep up with my email on a daily
basis, personal or other work matters can sometimes keep me away
from my email. If you contact me, but don't hear back for more than a week,
it is very likely that I am excessively backlogged or the message was
caught in the spam filters. Please don't hesitate to resend a message if
you feel that it did not reach my attention.
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3 comments
3 participants
participants (3)
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Andy Schwartz -
Dan Allen -
David Geary