OO Design Question (VB.Net)

[obfuscatr]

I have an application class, and a small class for a data item, that just holds about 10 variables and has a few basic functions that work on those variables.

I need functionality to load data received from outside (e.g. an XML file, or a database row) into an instance of the data class, and I can't decide where that functionality should go. Should the external data format be hidden from the data class and the functionality for loading the XML/db data be in the application class, or should the data class usefully be able to load data passed to it in native XML/ADO RS/other format?

What I have at the moment is an overloaded method on the data class that can receive different types of data, which it loads into itself, something like

class Data

Overloads Public Sub Load (XMLData as XMLDoc)

...

Overloads public Sub Load (DBData as ADO.RecordSet)

What's the 'correct' way to structure something like this?

Thanks

[MichaelW]

You should have another intermediate class that handles the source formatting for you. Your application and data item classes should remain encapsulated for the specific task. This way if you want to add, substract, or modify a format protocol later you can edit the new class and not have to change code in the other two and recompile, debug, etc.... That is assuming that you mandate your new class to format input data to be have the same end result everytime so your data class never has to change to handle any new format. Your new class will take care of that for you.

[obfuscatr]

Ok, so in terms of the code structure, is this how I'd lay that out:

class Application

Sub GettingSomeData

If (Data is from database) then

Dim Foo as new DataClass = DataHandlerClass.LoadData(DataRow)

If (Data is XML) then

Dim Foo as new DataClass = DataHandlerClass.LoadData(XML)

end sub

end class


class DataHandlerClass

OverLoaded Sub LoadData(Data as RecordSEt)

... (Load Data from Recordset) ...
Return DataClass

OverLoaded Sub LoadData(Data as XML)

... (Load Data from Recordset) ...
Return DataClass

end class

class DataClass

...

end class

[MichaelW]

Yes. Now your formatting process is independent of your app and DataClass and "blackboxed". Much easier to update and maintain.


If you truly wanted to make code updates easier yo could make each class an assembly and link them so after you go into production and needed to make updates to a specific class you would not have to recompile the whole app. If you app is fairly small and simple this approach would not achieve much benefit however.