Guessing game

Richard Gaskin ambassador at fourthworld.com
Tue Apr 3 13:05:56 EDT 2018


David Bovill wrote:

 > The use-case I had was to replace send syntax with the more elegant
 > set the ... of object to syntax.

While the getProp and setProp handlers would seem to lend themselves to 
a lot of useful object binding opportunities, they require caution: 
they're treated by the engine as system messages, and as such are not 
immune to the effects of lockMessages the way custom handlers are.

Systems depending on getProp and setProp will need to monitor 
lockMessages carefully to insure critical triggers are received as expected.

Using getter and setter accessor handlers avoids that concern, with a 
stylistic difference that isn't much more verbose:

   set the BeautifulColor of cd 1 to "light-grey"

-vs-

   dispatch SetBeautifulColor to cd 1 with "light-grey"

It doesn't read as nicely, but given that the trade-off can be 
unpredictability I'll take what I can get. :)

And depending on usage context, in many cases the UI event that 
initiates a calling chain may be on the card in question, not requiring 
out-of-message-path dispatching, making the call simpler than a property 
setting:

    SetBeautifulColor "light-grey"

For virtual objects like models, accessors can simplify things by not 
requiring that they be bound to a physical object which need not 
otherwise exist.  The name-value-pair programming we enjoy with custom 
props applies equally well with any array.  But with arrays we can have 
deeper levels, and are more easily savable/transportable than an object 
bound to a stack file.

-- 
  Richard Gaskin
  Fourth World Systems
  Software Design and Development for the Desktop, Mobile, and the Web
  ____________________________________________________________________
  Ambassador at FourthWorld.com                http://www.FourthWorld.com




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