Re: Child objects inheriting property values

You would be right Ryan if you are describing the 'inheriting'  of property
values. Not the explicit assignment of a value in a base to its child.
Well, Julian, it actually matters where the value comes from. Because all
you'd need to do is to have only one protected field in the base with an
initial value. You need not have another property of the same name in the
inheriting object.

instead of

this.delimiter = base.delimiter;

just have a
protected string delimiter = "<default_delimiter>";  // and you're done.

Julian raises an interesting twist with the concept of columns and records
and does not think that any of the two has to be semantically more upstream
than the other. I'll like to hear more on that. I hope we commonly agree
that every model has to be based on some assumption of domain context for it
to have semantic relevance to the problem it tries to solve. And our
assumption is that a record of facts is an aggregate collection of fields
(columns) of information that comprise that record (like on a paper form).
Even in a spreadsheet, a cell can be an intersection of a column and a row.
But once you talk about a record, whether on a paper file or on a database
or excel or cobol data structures, you would logically create a structured
record after you have first carved out the fields (columns) on the form.
Moreover, a record cannot be a type of a column or vise versa.

Please tell us what we are missing.
P


--------------------------------------------------
From: "Julian Lawrence" <[email protected]>
Sent: Friday, November 23, 2007 11:53 AM
To: <[email protected]>
Subject: Re: [DOTNET-CLR] 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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