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From Peter Donald <dona...@apache.org>
Subject Re: DataType interface?
Date Sun, 03 Jun 2001 15:12:45 GMT
At 11:53 PM 6/3/01 +1000, Conor MacNeill wrote:
>I have considered there to be three components to a datatype.
>1. The task level element used to create values of the datatype
>
>  <fileset name="foo" .../>
>
>2. The nested element used to create an instance of the datatype within the
>context of another task
>
>   <fubar ...>
>       <fileset .../>
>   </fubar>
>
>3. The type which is actually stored in the ExecutionFrame when a value of
>the datatype is created (Sorry for the mutant terminology).
>
>Now, I consider that 1 and 2 must be the same class since any way I can
>configure a top level datatype value I should be able to configure that
>datatype when nested in another task. 

I actually see 2+3 as being same class while 1 is a separate case. Mainly
as top-level tasks have attributes that I don't believe all datatypes
should have (ie name or ant:id) and they also have a whole host of baggage
that comes along with it (ie why does a FileSet need an execute() method).
With some tricky manipulation of TaskModel we can make this task relatively
easy to do.

>So, what is the requirement for the core to distinguish a datatype and the
>element which is configured from the project model? How will the core
>manipulate the datatype at the abstract level - i.e. can something treat
>the datatype as just a datatype without knowing it is actually some
>specific class. If the user of the datatype needs to know it is some
>specific class, eg FileSet, then the same class can be used.

I am not sure there needs to be any special treatment of "datatypes" in the
way you mention. The only special treatment I can see is for next point...

>I'm also not sure why we need a DataType registry. Isn't the associated top
>level task sufficient?

So people can implement a generic task like

<set name="foo">
  <fileset ... />
</set>

Having each DataType have a separate task to assign it can be tedious when
you have a high number of datatypes - one of my usecases contains about 17+
datatypes and I don't want to create 17+ tasks to wrap them ;)
Cheers,

Pete

*-----------------------------------------------------*
| "Faced with the choice between changing one's mind, |
| and proving that there is no need to do so - almost |
| everyone gets busy on the proof."                   |
|              - John Kenneth Galbraith               |
*-----------------------------------------------------*


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