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From: Ray Blaak <blaak@infomatch.com>
Subject: Re: From extended Pascals to Ada 95 guide
Date: 2000/08/28
Message-ID: <u8zthkvnz.fsf@infomatch.com>#1/1
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Newsgroups: comp.lang.ada,comp.lang.pascal.misc
Date: 2000-08-28T00:00:00+00:00
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Al Christians <achrist@easystreet.com> writes:
> If I define my own type in a Pascal program and want to save it in
> one of the VCL containers, the code would look like this:
> 
>     { To Insert }      AContainer.Objects[i] := Pointer(MyObject);
>     { To Retrieve }    MyObject := TMyObject(AContainer.Objects[i]);
> 

With Delphi, I have always found it worthwhile to make my own container
classes that do the appropriate checking:

type MyContainer = class
public
   procedure Insert(atIndex : Integer; obj : MyObject);
   function GetAt(index : Integer) : MyObject;
private
   flist : TList;
end;

where we have:

procedure MyContainer.Insert(atIndex : Integer; obj : MyObject);
begin
  flist.Items[i] := Pointer(obj);
end;

function MyContainer.GetAt(index : Integer) : MyObject;
begin
  result := MyObject(flist.Items[i]);
end;

and then I can do:
   
   AContainer.Insert(i, MyObject);
   MyObject := AContainer.GetAt(i);

Now I have the benefit of good typechecking. The one disadvantage of this
approach is that Delphi's lack of generics can mean constructing these wrapper
classes is tedious. However, the benefit outweighs the tedium, in my opinion.

-- 
Cheers,                                        The Rhythm is around me,
                                               The Rhythm has control.
Ray Blaak                                      The Rhythm is inside me,
blaak@infomatch.com                            The Rhythm has my soul.