On Mar 29, 2007, at 8:42 AM, Richmond Mathewson wrote:
1. So let's have a merry drop-down button on the Main
Stack to change units.
2. on mouseUp
the mouseLine
if it is "inches" then
do FANCY CONVERSION ROUTINE NUMBER 999
end if
end mouseUp
where FANCY CONVERSION ROUTINE NUMBER 999 pushes all
the values contained in all the list fields on the
main stack and all the substacks through the required
algorithm to convert (say) millimetres to inches.
Hi Richmond (sorry, this somehow turned into a long post),
While there is nothing difficult about the example you provide above,
I see a broadcasting system (like the one Dave has talked about) as
making your code cleaner and easier to read.
The above example only changes the property in once place (as is
common for many application preferences). But there are some
scenarios where you can change a property of an object from multiple
locations. For example, if I wanted to change the title of an image
in an image cataloging application I might have a command like the
following:
image_setProp theImageObject, "title", theNewTitle
-- Without Broadcasting --
Using your technique above you might then add a second call which
updated the title of the image anywhere it appeared in the program
(maybe in a thumbnail window and an editor window) so you end up with
something like this anywhere you want to change the title:
image_setProp theImageObject, "title", theNewTitle
UpdateImageAnywhereItAppearsInProgram theStepControl
-- With Broadcasting --
Using broadcasting, you could register the thumbnail window and the
editor window to receive messages whenever the "title" property of a
image was updated using a handler that might be defined as follows:
object_addPropertyListener pObject, pProperties, pTargetObject, pMessage
And in practice might be called like this when a new image was created:
object_addPropertyListener theNewImageObject, "title", the long id of
stack "ThumbnailViewer", "ImagePropertyUpdated"
object_addPropertyListener theNewImageObject, "title", the long id of
stack "Editor", "ImagePropertyUpdated"
Now in my code I can just set the image title from anywhere I would
like (using image_setProp) and I know that it will be updated
everywhere in the program. I don't have to remember to set the title
and then call another function to update windows everywhere.
-- Implementing Broadcasting --
Some development environments, like Flash, have built-in broadcasting
support. Revolution does not so you end up having to create your own
libraries to handle it. While this is a little more effort at first
to write the library it really pays off for folks who prefer the
broadcasting approach.
For example, in the "image_setProp" handler (which can be used to set
any number of properties) you would then have the following call near
the end of it's definition which would handle broadcasting the
changed property to any "listeners":
on image_setProp pControlReference, pProperty, pValue
## DO WHATEVER TO STORE PROPERTY
....
## BROADCAST PROPERTY CHANGE
object_broadcastPropertyChange pObject, pProperties
end image_setProp
In the end you are getting the same behavior. I happen to think
broadcasting is a cleaner way of approaching the problem and use that
approach in my projects as well.
--
Trevor DeVore
Blue Mango Learning Systems
www.bluemangolearning.com - www.screensteps.com
[EMAIL PROTECTED]
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