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From: Stefan Muehlebach <ia94mueh@htl-bw.ch>
Subject: Overlaying of methods.
Date: 1997/09/30
Message-ID: <34310F93.41C6@htl-bw.ch>#1/1
X-Deja-AN: 276718966
X-Complaints-To: news@ubnnews.unisource.ch
X-Trace: ubnnews.unisource.ch 875623498 24452 (None) 147.86.130.106
Organization: Technical University of Brugg-Windisch - Switzerland
Newsgroups: comp.lang.ada
Date: 1997-09-30T00:00:00+00:00
List-Id: <comp.lang.ada>


Hello.
I have a problem with objects and inherited methods. I have two classes,
declared in two seperated packages, on inherited from the other. Both
declare their own 'Init' procedures.

Part of the first package:

  type XaCrowColumn     is new XaContainer with private;
  type XaCrowColumn_Ptr is access all XaCrowColumn'class;
  procedure Init(o           : access XaCrowColumn;
                 parent      : access XaApplication'class;
                 orientation : ...;
                 num_cols    : Integer := 1;
                 adjust_last : Boolean := True);

(XaApplication is the parent class for all classes in my library)

Part of the second package (which uses the one above):

  type XaCradioBox     is new XaCrowColumn with private;
  type XaCradioBox_Ptr is access all XaCradioBox'class;
  procedure Init(o           : access XaCradioBox;
                 parent      : access XaApplication'class;
                 orientation : ...;
                 num_cols    : Integer := 1);

In the main program I declare a new object the following way:

  myRadioBox: XaCradioBox_Ptr := new XaCradioBox;

BUT - and that is the frustrating point - if I write a statement like
this

  Init(myRadioBox, aParent, anOrientation);

not the method in the second package is called but the one in the first!
Although the first parameter is of type XaCradioBox. Why?
I found out, that if I remove the defaults or write the same parameter
list for both 'Init'-procedures every thing is ok.

The question is also in which way does Ada look for an appropriate
method.

If someone could help me or at least verify my problem I would be very
happy.