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From: gus@plains.UUCP (jim gustafson)
Newsgroups: comp.lang.pascal
Subject: Re: (one way to) Copying objects in Turbo Pascal 5.5
Message-ID: <4878@plains.UUCP>
Date: 25 May 90 08:09:15 GMT
Organization: North Dakota State University  Fargo, ND
Lines: 57

>I'd like to have a constructor for an object that just copies another instance
>of it or one of its descendants, and (the hard part) also copies the type
>information.  

Here's one way to get part of what you want.
(the 'new' constructor could have been 'Init')
-----------------------------------------------

PROGRAM TestCopy(Input, Output);

TYPE
    ClassTest = OBJECT
        a, b : CHAR;

        CONSTRUCTOR new;
        CONSTRUCTOR copy(VAR oldInstance:ClassTest);
        PROCEDURE   print;
    END;

    ClassTest2 = OBJECT(ClassTest)
        x, y : INTEGER;

        CONSTRUCTOR new;
        PROCEDURE   print
    END;

CONSTRUCTOR ClassTest.new;
BEGIN a:= 'a';  b:= 'b' END;

CONSTRUCTOR ClassTest.copy(VAR oldInstance:ClassTest);
BEGIN
    self:= oldInstance
END;

PROCEDURE ClassTest.print;
BEGIN Writeln('ClassTest.a is  ''', a, ''' ClassTest.b is  ''', b,'''') END;

CONSTRUCTOR ClassTest2.new;
BEGIN x:= 0;  y:= 1 END;

PROCEDURE ClassTest2.print;
BEGIN Writeln('ClassTest2.x is ''', x, ''' ClassTest2.y is ''', y, '''') END;


VAR
    aTest2, aCopyOf2 : ClassTest2;
BEGIN
    aTest2.new;
    aTest2.print;

    aCopyOf2.copy(aTest2);
    aCopyOf2.print;
END.
-- 
Jim Gustafson			UUCP:     uunet!plains!gus
North Dakota State University 	Bitnet:	  gus@plains
Fargo, North Dakota 58105	Internet: gus@plains.nodak.edu