Again with the start using.

[Richard Gaskin]

Rob Cozens wrote:

> Serendipity Library's libraryStack handler not only checks to see if it 
> is the target of the message, it also checks the state of a local 
> variable to determine if libraryStack has already run once.  [I don't 
> want to reinitialize variables once the library is in use:]

A good choice, sorely absent from my example but well worth doing.

> Note I do NOT pass libraryStack unless the target is not Serendipity 
> Library, as I see nothing going on that other libraries need to know 
> about.  And if they do need to know if Serendipity Library is in use, 
> they can check the stacksInUse property.

While for most practical purposes there will not likely be any other 
library or backscript that would need to know when a libraryStack 
handler is sent to your library, it is a possibility.  While admittedly 
unlikely, over the years I've come to regard "unlikely" as "possible", 
and "possible" as "will happen sooner or later".  I've found a majority 
of issues in using my work in other people's environments stem from 
making assumptions about the environment, which has led to my personal 
policy of always preserving the native state of things wherever I have 
the opportunity to do so.

Requiring polling the stacksInUse is less efficient for that purpose, 
but on balance if another stack needs an event-driven method the best 
place for that might be in a frontScript anyway.

Given that a library should always perform those two checks anyway (to 
see if it is the target of the message and whether it's been initialized 
already), what is the downside to passing that system message just as 
one would usually want to pass all others?

--
  Richard Gaskin
  Fourth World Media Corporation
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