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From: Lawson.English@p88.f15.n300.z1.fidonet.org (Lawson English)
Newsgroups: comp.sys.mac.programmer
Subject: ThinkC TCL's DoCommand() wish
Message-ID: <13514.28538C9C@stjhmc.fidonet.org>
Date: 8 Jun 91 01:07:43 GMT
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Larry Weinberg writes in a message to All

LW>  Why insn't it implemented as: 
LW>  CBureaucrat::DoCommand(long theCommand, long data) 
LW>  (data could be a pointer to any type of structure that might 
LW> be  needed) 
LW>  Am I alone with this wish? Since I don't have this feature, 
LW> and I don't want to modify the TCL sources because I want to 
LW> remain compatible, I create special methods for subclasses that 
LW> I call directly, hence I must cast explicitly to a given subclass 
LW> therefore loosing some of that beautiful object oriented generality 
LW> of not having to know what type of object I am passing a message 
LW> on to.  Am I missing something obvious? Is there some truer message 
LW> passing scheme implemented in the Class Library's chain of command? 
LW> Or should I take the plunge and modify the CBureaucrat class 
LW> and have problems with future versions

One thing that you could do is implement a "gCommandDataPtr" global variable.
Whenever you wish to pass auxilliary data up the chain of command, set this
variable to your dataPtr. Any command that expects extra data could check this
global and set it to nil/null when it is done (if it's already nil/null then
no data was passed). You could have a change to yourApplication's DoCommand
that would set the ptr to nil/null if it yourApplication's DoCommand was reached
with a non-sensical command. This is a little kludgey but obviates (whataword)
the need to rewrite the TCL's.


Lawson
 

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