The basic difference is this:
Behaviors are intended to be "attached" to sprites. When the
playhead enters the begining of a sprite span that has a behavior
attached, Director calls the "on beginSprite" handler in the
behavior. Inside a behavior, you can also code up a special handler
called "on getPropertyDescriptionList", that allows you - at
authoring time - to set the value for properties used in the
behavior. The settings of these property values are saved in the
score. This way, the same behavior can be used in multiple places,
and you can have different initial values for any or all properties
in the behavior (as defined by your getPropertyDescriptionList).
When the playhead reaches the end of a sprite span, Director calls
the "on endSprite" handler.
Parent scripts are not intended to be "attached" to sprites. A
programmer creates an object explicitly from a parent script by
calling the "new" handler in the script. The "new" handler in the
parent script typically looks like this:
on new me <, someOptionalParameters>
-- any initialization code you want to have
return me -- this returns the object reference "me"
end
You create an object by executing a line of code like this:
someObjectReference = new(script "SomeParentScript",
<someOptionalParameters>)
This returns the "object reference" to the newly created object.
Whenever you want to call any of the handlers in the object, you must
supply this object reference, for example
mDoSomething(someObjectReference, <someOptionalParameters>)
This calls the mDoSomething handler within the object referred to by
someObjectReference, and will pass someOptionalParameters if you need
to. When you are finished using an object, you must explicitly get
rid of the object by setting the object reference to some new value,
for example:
someObjectReference = VOID
Hope that helps. The fact that behaviors can also have a "new"
handler, and the explanation of the affect of ancestors is not
important to the basic understanding of the difference between
behaviors and parent scripts.
Basic difference: Behaviors are intended to be attached to sprites -
beginsprite and endsprite handlers called automatically, and you can
use GPDL. Parent scripts only create objects when you as the
programmer explicitly call the new handler, objects "live" until you
kill them by setting the object reference (and any copies of the
object reference) to VOID (or 0, or anything else).
Irv
At 10:53 AM -0500 12/3/01, Genevieve Young wrote:
>Thanks to Kerry, James and Luke for taking the time and trouble to reply.
>
>
>Let me try to understand what you are all trying to say.
>
>a. When I use on new() me,none of the properties set in the
>ongetPropertyDescriptionList are available, so I can't use the on
>GPDL?
>
>b.Why does Kerry write then that both will execute if you have both?
>In ancestor scripts it may or may not execute. Yet James writes
>that you need an explicit Lingo call to create a new instance of a
>parent script.
>
--
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