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From Jeff Turner <j...@socialchange.net.au>
Subject RE: Dynamic binding of properties
Date Thu, 05 Oct 2000 07:01:57 GMT


On Thu, 5 Oct 2000, Conor MacNeill wrote:

> Jeff,
> 
> Properties are still immutable but can be bound in a target rather than at
> parse time. So we are vaguely dynamic.
> 
> Mutability is easy to introduce but then prevents a build's property values
> from being set externally.

Oh I see.. the build.xml property definition would always overwrite
the external definition.

> One thought is to associate a priority value with
> each property and only allow it to be changed at the same or higher
> priority. That introduces mutability with precedence. Personally I think it
> is the way to go.

I like it.. I was just about to propose an extra property attribute:

<property name=".." value=".." overrides="true"/>

when I realised that "overrides" is just binary priority.

One thing; you said "at the same or higher priority". If the default
priority is 0, then for backwards compatibility, properties should only be
overridden by -higher- priorities.

--Jeff

> 
> Conor
> 
> 
> --
> Conor MacNeill
> conor@cortexebusiness.com.au
> Cortex eBusiness
> http://www.cortexebusiness.com.au
> 
> > -----Original Message-----
> > From: Jeff Turner [mailto:jeff@socialchange.net.au]
> > Sent: Thursday, 5 October 2000 16:55
> > To: ant-user@jakarta.apache.org
> > Cc: Scott M Stark
> > Subject: Re: Dynamic binding of properties
> >
> >
> >
> >
> > On Thu, 5 Oct 2000, Peter James Donald wrote:
> >
> > > On Wed, 4 Oct 2000, Scott M Stark wrote:
> > > > I tried to write an ant script that would go through an
> > object serialization compatibility
> > > > testing suite. It is using BSF/JavaScript to try to simplify
> > the writing of a common set
> > > > of steps shown below as the runV target. The script below
> > does not work because
> > > > properties are bound as the xml document is parsed. Now I
> > have looked at how
> > > > properties are handled by Ant and at first glance it does not
> > seem that it would be
> > > > all that difficult to introduce dynamic properties, but it
> > would require a complete
> > > > change in how properties and attributes are represented. Is
> > this something that
> > > > could show up on a future todo list or are there
> > ramifications that would make this
> > > > unlikely?
> > >
> > > It is in progress now and will eventually go to fully
> > > dynamic evaluation I believe. It is doing partial dynamic
> > > evaluation now so you may want to download latest CVS as
> > > that *may* solve your problem (don't know haven't updated
> > > from CVS since it was added)
> >
> > I don't think it's got very far. Using the latest CVS, the following:
> >
> > <property name="base" value="."/>
> > <echo message="base is ${base}"/>
> > <property name="base" value="foo"/>
> > <echo message="base is ${base}"/>
> >
> > Just prints:
> >
> > main:
> > base is .
> > base is .
> >
> > --Jeff
> >
> > >
> > > Cheers,
> > >
> > > Pete
> > >
> > > *--------------------------------------------------*
> > > | Latrobe University,     | Does the name 'Pavlov' |
> > > | Bundoora, Australia     |    ring a bell ?       |
> > > *--------------------------------------------------*
> > >
> > >
> >
> >
> 
> 


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