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From: anders@verity.com (Anders Wallgren)
Newsgroups: comp.sys.mac.programmer
Subject: Re: MacApp & C++ destructors
Message-ID: <1991Apr14.015647.3521@verity.com>
Date: 14 Apr 91 01:56:47 GMT
References: <1991Apr10.210516.25812@rice.edu> <9827@etsu.CMI.COM> <1991Apr13.235903.26110@ux1.cso.uiuc.edu>
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Reply-To: anders@verity.com (Anders Wallgren)
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In-Reply-To: mlanett@yoyodyne.ncsa.uiuc.edu (Mark Lanett)

You probably shouldn't use constructors and destructor with classes
descended from TObject unless you know that they will always be
created with new.  I know for a fact that objects instantiated by name
(ie., from a 'view' resource) then the constructor will NOT be called,
since Object Pascal knows nothing about C++ constructors.  I wouldn't
be surprised if there was a similar problem with destructors that
means you just can't use this C++ feature (don't despair - MacApp 3.0
is being written in C++).

MacApp/Object Pascal uses initializers and free methods.  Every class
descended from TObject has an Initialize method - use this to get your
object into a freeable state in case something goes wrong later in the
initialization stage.  The IYourClass method usually calls it's
superclasses IMySuperClass method and then does it's own
initialization.  Of course, if the object is being instantiated from a
view resource, then IRes is used instead of IYourClass.

This is one of the penalties of using an Object Pascal library from
C++ - you also can't use multiple inheritance and I think overloading
is also a no-no.

anders