The question I want to ask is thus: Is casting down the inheritance tree (ie. towards a more specialiased class) from inside an abstract class excusable, or even a good thing, or is it always a poor choice with better options available? Now, the example of why I think it can be used for good. I recently implemented Bencoding from the ...
I'm designing a web site navigation hierarchy. It's a tree of nodes. Most nodes are pages. Some nodes are links (think shortcuts in Windows). Most pages hold HTML content. Some execute code. I'd like to represent these as this collection of classes and abstract (MustInherit) classes This is the database table where I'm going to ...
I am making a game in C++ and am having problems with my derived class. I have a base class called GameScreen which has a vitrual void draw() function with no statements. I also have a derived class called MenuScreen which also has a virtual void draw() function and a derived class from MenuScreen called TestMenu which also has a void ...
I've kind of backed myself into a corner here. I have a series of UserControls that inherit from a parent, which contains a couple of methods and events to simplify things so I don't have to write lines and lines of near-identical code. As you do. The parent contains no other controls. What I want to do is just have one event handler, ...
I'm looking for a good, clean way to go around the fact that PHP5 still doesn't support multiple inheritance. Here's the class hierarchy: Message -- TextMessage -------- InvitationTextMessage -- EmailMessage -------- InvitationEmailMessage The two types of Invitation* classes have a lot in common; i'd love to have a commo...
I am trying to use forms authentication with Active Directory but I need roles (memberOf) from AD. I am trying to override members of RoleProvider to make this possible (unless someone knows of a better way). I am stuck on an error in the new class that is inheriting from RoleProvider. The error is: ADAuth.ActiveDirectoryRoleProvider' d...
When you use composition, then you can mock the other objects from which your class-under-test depends, but when you use inheritance, you can't mock the base class. (Or can you?) I generally try to prefer composition over inheritance, but sometimes inheritance really seems like the best tool for the job - well, at least until it comes t...
Is it possible under any set of circumstances to be able to accomplish this? My current circumstances are this: public class CustomForm : Form { public class CustomGUIElement { ... public event MouseEventHandler Click; // etc, and so forth. ... } private List<CustomGUIElement> _elements; .....
Everything inherits from object. It's the basis of inheritance. Everything can be implicitly cast up the inheritance tree, ie. object me = new Person(); Therefore, following this through to its logical conclusion, a group of People would also be a group of objects: List<Person> people = new List<Person>(); people.Add(me); people.Add(...
I want to extend the basic ControlCollection in VB.NET so I can just add images and text to a self-made control, and then automaticly convert them to pictureboxes and lables. So I made a class that inherits from ControlCollection, overrided the add method, and added the functionality. But when I run the example, it gives a NullReferenc...
The non-virtual interface idiom describes how the virtual methods are nonpublic customisation points, and public methods are nonvirtual to allow the base class to control at all times how the customisation points are called. This is an elegant idiom and I like to use it, but how does it work if the derived class is a base class in itse...
What are the C++ rules for calling the superclass constructor from a subclass one?? For example I know in Java, you must do it as the first line of the subclass constructor (and if you don't an implicit call to a no-arg super constructor is assumed - giving you a compile error if that's missing). ...
I'm not sure if this is a strange thing to do or not, or if it is some how code smell...but I was wondering if there was a way (some sort of oop pattern would be nice) to "cast" a base type to a form of its derived type. I know this makes little sense as the derived type will have additional functionality that the parent doesn't offer wh...
If I have a subclass that has yet to implement a function provided by the base class, I can override that function and have it throw a NotSupportedException. Is there a way to generate a compile-time error for this to avoid only hitting this at runtime? Update: I can't make the base class abstract. ...
This is likely going to be an easy answer and I'm just missing something, but here goes...If I have a Type, (that is, an actual System.Type...not an instance) how do I tell if it inherits from another specific base type? ...
Forgive the vague title, I wasn't sure how to describe it. If you have a generic model "Archive", how do you show different views/forms based on a user selected 'type'? For example, the user creates a new "Archive", then gets the choice of video, book, audio etc. From there they get different forms based on the archive type. Or would ...
Why can't I create a class in VB.NET that inherits System.IO.Directory? According to Lutz Roeder, it is not declared as NotInheritable! I want to create a utility class that adds functionality to the Directory class. For instance, I want to add a Directory.Move function. Please advise and I will send you a six pack. OK nevermind I'm...
I am working with a log of events where there are about 60 different "types" of events. Each event shares about 10 properties, and then there are subcategories of events that share various extra properties. How I work with these events does depend on their type or what categorical interfaces they implement. But it seems to be leading t...
In other words, is it correct to use: public class CustomerList : System.Collections.Generic.List<Customer> { /// supposed to be empty } instead of: using CustomerList = System.Collections.Generic.List<Customer> I'd rather use the first approach because I'd just define CustomerList once, and every time I needed a customer list ...
I have created my own Tree implementation for various reasons and have come up with two classes, a 'base' class that is a generic tree node that is chock full of logic and another class that extends that one which is more specialised. In my base class certain methods involve instantiating new tree nodes (e.g. adding children). These ins...