Re: Child objects inheriting property values

Fascinating question.

It seems to me that there's a considerable conceptual difference between
inheriting properties and inheriting values of properties.

Class inheritance isn't always an indicator of the sequence in which
classes should be instantiated.

During instantiation it really shouldn't matter where the value of a
property comes from. If it happens to be the value of a property of an
instance of the base class or default to a value provided in the base
class during construction so be it. Why should it be disallowed in the
compiler?

The flexibility is probably required more in abstracted than literal
models. To expand a little. The constraining idea of columns and records
is an artefact of database paradigms. To those who think in spreadsheet
cells, which can be grouped any which way, it may seem odd to have to
worry whether the row or the column is created first. Nothing right or
wrong or absolute about the two paradigms, just different models, and
there are others.

The practical solutions to the question were described in the first
couple of posts.

Julian

> -----Original Message-----
> From: Discussion of development on the .NET platform using
> any managed language [mailto:[email protected]]
> On Behalf Of Ryan Rinaldi (TT)
> Sent: Saturday, 24 November 2007 1:19 AM
> To: [email protected]
> Subject: Re: [DOTNET-CLR] Child objects inheriting property values
>
>
> "Moreover, assigning field values of a base class to its
> subclass in a constructor feels awkward. A good compiler
> should disallow it."
>
> If any .NET compiler disallowed it ASP.NET wouldn't work! :)
> At least the older ASP.NET Web Application code-behind model.
>  In the code behind you declare all of the controls while the
> .aspx page instantiates them.  Quite awkward and convoluted
> resulting in a page that can compile but if you forget to add
> the control to the page it crashes at runtime.
>
> -----Original Message-----
> From: Discussion of development on the .NET platform using
> any managed language [mailto:[email protected]]
> On Behalf Of Peter Obiefuna
> Sent: Wednesday, November 21, 2007 9:40 PM
> To: [email protected]
> Subject: Re: [DOTNET-CLR] Child objects inheriting property values
>
> Using inheritance is semantically wrong since a Column 'IS A'
> record is not correct. Moreover, assigning field values of a
> base class to its subclass in a constructor feels awkward. A
> good compiler should disallow it. Again, the class order in
> your question appears reversed to me (I expect a column
> collection to exist before a record does) but I'll just
> answer your question narrowly. Here's my solution to that
> problem. =======================================
>
> class Column{
>
>     private char delimiter;
>     public Column(){
>         // first, set parent record;
>         // then ...
>         this.delimiter = ParentRecord.Delimiter;
>     }
>     public Record ParentRecord { get; set; }
>     public char Delimiter { get; set; }
> }
>
> class Record{
>     private char delimiter = '^';
>     public Record(){
>
>     }
>     private Column[] columns;
>     public char Delimiter {get; set;}
>
> }
>
> --------------------------------------------------
> From: "Adrian Martin" <[email protected]>
> Sent: Tuesday, November 20, 2007 6:28 AM
> To: <[email protected]>
> Subject: Re: [DOTNET-CLR] Child objects inheriting property values
>
> >        class Column : Record
> >        {
> >                public Column()
> >                {
> >                        this.Delimeter = base.Delimeter;
> >                }
> >        }
> >
> >
> >
> >
> >
> >
> >
> > -----Original Message-----
> > From: Discussion of development on the .NET platform using
> any managed
> > language [mailto:[email protected]] On Behalf Of Brady
> > Kelly
> > Sent: 20-November-2007 10:10
> > To: [email protected]
> > Subject: Child objects inheriting property values
> >
> > I have a hierarchy of objects that share some attributes,
> e.g. both my
> > parent Record and Column objects have a columnDelimiter
> property.  I
> > want this property on the Column object to default to the same
> > property on the
> > Record object, until specified on the Column object.  What
> is the best
> > way
> > to go about this?  I could give each Column a reference to
> the Record
> it
> > belongs to, but this seems not quite right to me.  My other
> option is
> to
> > have the Record act as a ColumnFactory, setting the columnDelimiter
> > value on each Column it creates, until a set accessor on Column
> > optionally overrides
> > that default value.
> >
> >
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