Hi Again Chipp!
I just thought of something else. Apart from using ISM as a message
broadcast system, it can also be used as a central place to hold
system wide (or inter-stack) data.
On 28 Mar 2006, at 11:01, Chipp Walters wrote:
David,
Also, I see where you're using custom props to hold non-permanent
data. While this is OK, I prefer to use library stack locals, as
these zero out when the app quits. That way you don't have to
explicitly reset them. I like customProps for data which may have
to be saved between sessions...just my 2 cents.
ISM has a concept of persistent data which remains across application
launches (in a standalone) or across launches of the IDE.
As an example of this, take a Preferences Stack (a separate Prefs.rev
file).
The user launches the standalone which takes them to the main
application stack (call it AppMain.rev), this in turn allows them to
select the preference stack. The user some system-wide preference
(say the language is changed from English to Spanish). The preference
stack sends a message ("LanguageChanged", "LanguageKindDefault",
"Spanish") and all listening objects get the message and change
themselves so that they now set their text to the new language).
However since only AppMain.rev is "listening" it is the only stack to
change.
The user now closes the Preferences Stack and Quits the App (or a
developer quits the IDE).
The App is relaunched, the current stack (AppMain.rev) is set to
Spanish. The user now does something that calls up another stack like
double clicking on a thumbnail of an image so as it see it in an
ImageViewer/Editor (call this stack ImageEdit.rev). The language is
still English in the (mageEdit.rev stack (or more accurately it's the
language that was last chosen from the Preferences Stack when
ImageEdit.rev was last open).
Normally you'd have to do something like call up the Preferences
Stack (maybe making it invisible) so that it can re-send it's data)
or have the Stack with the new data somehow send it to the new
stack . However, in ISM if you make the data persistent, as soon as
an Object(s) starts "listening" they get sent the data from the last
time it was set, in this case "Spanish". The Preferences Stack
doesn't have to be re-opened and there is no extra initialization
code needed anywhere. The same path that handles a change also
handles the initialization!
So, in order to do this, I need to store persistent data in a custom
property. I intend hold this information in locals while the App is
running and copy it into Custom Properties in the ISM stack when the
last stack de-registers itself. That way I get the best of both worlds!
All the Best
Dave
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