Saving substacks in stand alones
jspencer78 at mac.com
Sat Mar 13 14:40:50 CST 2004
Newbie question just so I can understand what is happening. I'm not
understanding how message passing works or how "this" works in the
context of substacks.
I've got some old stuff I'm converting to Rev. standalones to run under
OS X and I've been wandering through the example Employee Data Base
just to see how it is being done. Being Unix based, the standalone
can't save itself so I understand why a separate stack is used. This
separate stack, while cloned from the main stack is a completely
separate file. The main stack opens or creates this separate data
stack, brings it to the front and hides itself (the main stack). So
far so good.
What I don't get is how the file saving code works. The menu handler
for file menu items in the data stack is in the card script for the
currently displayed card; the Save menu choice calls doFileSave. There
is no doFileSave in the card script nor in that card's stack so it ends
up going to the "main" stack where it is executed. The file itself
gets saved in the "main" stack's script where the handler calls, after
some setup stuff:
save this stack
What I don't get and hope that some kind soul will tell me is:
a) Considering that the data stack is not a substack of the main stack
but rather is a completely separate entity in its own file, why does
the doFileSave message get sent to the main stack? I can surmise that
the main stack of a stand alone application is always in the message
chain but that doesn't explain to me why that works even within the
Revolution Environment where I can have lots of stacks open.
b) How does the "this" work in the line above? Does "this stack" refer
to the stack from which the message was sent?
Thanks for the help.
James P. Spencer
jspencer78 at charter.net
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