Tagging certain objects with contact, copyright, etc

[Jeanne A. E. DeVoto]

At 6:35 PM -0700 2/7/04, Dar Scott wrote:
>I was thinking that for custom controls that require a supporting 
>library that some metadata would be allowed to come from the 
>library.  I have to think about whether this can still be done or 
>whether it is important.

A virtual property using a getProp handler could do this, something like:

   getProp metaData[myPropertyName] -- "metaData" is the custom prop set name
     if myPropertyName is "libVersion"
     then return the someCustomProp of stack "Library" -- goes and gets it
     else pass metaData -- let the engine return the specified custom prop
   end metaData

In this case, the "libVersion" property isn't actually stored in your 
object; calling its value goes and queries the library stack.

>>It also makes it easy to enforce the "read-only" status with a 
>>setProp handler, without interfering with other custom properties 
>>or having to list all the read-only properties in a handler.
>
>Well, before you brought the custom property set idea, for each 
>metadata property I was thinking of (1) a setProp to ignore the set 
>(or optionally to change the value) and optionally (2) a virtual 
>getProp.
>
>However, I'm not sure how to do the "read-only" for a custom 
>property set or if it is important.

Here's an example. In this handler, "metadata" is the name of the 
custom property set that you want to make read-only:

   setProp metaData[myPropertyName]
     -- The myPropertyName parameter contains the name of
     -- the property that's being set
     beep
     exit metaData -- don't pass the setProp
     -- because the setProp trigger isn't passed, it
     -- doesn't reach the engine, and so the custom
     -- property you specified isn't set
   end metadata

The nice thing about putting all the read-only properties in a custom 
property set is that you don't need a switch or if/then statement to 
single out the read-only properties from the writeable ones.
-- 
jeanne a. e. devoto ~ jaed at jaedworks.com
http://www.jaedworks.com