Some taskdefs support an "if" attribute to control
their behavior (<fail> for example).  However, their
is not guideline, nor list, of which tasks support the
"if" (and "unless") attributes.

There have been efforts to integrate the "if" (and
"unless") logic into all taskdefs, but it has been
rejected repeatedly :-(

So, unless the ANT docs say that a given taskdef
supports the "if" attribute you are stuck with
wrapping the tasks with an <if> (from the ant-contrib
project) or calling them from a separate helper target
that uses the "if" attribute.

--- Rainer Noack <[EMAIL PROTECTED]> wrote:
> Hi Holger,
> 
> 1st: Ant properties can not be overwritten.
> 2nd: To set "conditional" property-values take a
> look at the <condition/>
> task.
> 3rd: if/unless are attributes of a target.
> 
> Try something like this:
> 
> <target name="set-props">
> <condition property="prop1"
> value="${basedir}/../..">
>   <isset property="certain.prop"/>
> </condition>
> <property name="prop1" value="${basedir}/.."/>
> </target>
> 
> Cheers,
> 
> Rainer
> 
> > -----Original Message-----
> > From: Holger Rauch [mailto:[EMAIL PROTECTED]
> 
> > Sent: Wednesday, April 06, 2005 11:33 AM
> > To: [email protected]
> > Subject: Overview on usage of if/unless attributes
> > 
> > 
> > Hi!
> > 
> > I'm aware that if/unless attributes can be used to
> select 
> > targets depending on whether the value of some
> property is 
> > set or not. Where else
> > (types/tasks) can if/unless be used in addition to
> targets?
> > 
> > Is there an overview on this issue in some place?
> > 
> > (I tried using "if" on <property> in order to set
> the value 
> > of a property dependet on whether another property
> is set. 
> > Reason was to avoid the rather lengthy fragments
> introduced 
> > by using ant-contrib's <if> task. Didn't work,
> however, so I 
> > guess I'm stuck with the <if> task, right?)
> > 
> > That's what I tried:
> > 
> > <property name="prop1" value="${basedir}/.." />
> > <property name="prop1" value="${basedir}/../.."
> if="certain.prop" />
> > 
> > Thanks in advance for any info/pointers!
> > 
> > Greetings,
> > 
> >     Holger
> > 
> >
>
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