I'm having some inheritance issues as I've got a group of inter-related abstract classes that need to all be overridden together to create a client implementation. Ideally I would like to do something like the following: abstract class Animal { public Leg GetLeg() {...} } abstract class Leg { } class Dog : Animal { public overrid...
I discovered that the cause of my problems (see question) was the lack of support in C# for covariance on inherited methods' return types. Now I'm curious what languages support this feature. Accepted answer will be whoever can name the most. EDIT: John Millikin correctly pointed out that lots of dynamic languages support this. I'll ...
What are the performance, security, or "other" implications of using the following form to declare a new class instance in PHP <?php $class_name = 'SomeClassName'; $object = new $class_name; ?> This is a contrived example, but I've seen this form used in Factories (OOP) to avoid having a big if/switch statement. Problems that...
I would like to implement something similar to a c# delegate method in PHP. A quick word to explain what I'm trying to do overall: I am trying to implement some asynchronous functionality. Basically some resource-intensive calls that get queued, cached, and dispatched when the underlying system gets around to it. When the asynchronou...
Why prefer composition over inheritance? What trade-offs are there for each approach? When should you choose inheritance over composition? ...
This caught my attention last night. On the latest ALT.NET Podcast Scott Bellware discusses how as opposed to Ruby, languages like c#, java et al. are not truly object oriented rather opting for the phrase "class-oriented". They talk about this distinction in very vague terms without going into much detail or discussing the pros and co...
I'm doing a research project, part of which is concerend with object oriented databases. I would like to hear from anyone who has experience using such databases, or considered using them but opted to go for a different approach. What did you like? What didn't you like? What made you choose using the approach you ended up using? When ...
Below I present three options for simplifying my database access when only a single connection is involved (this is often the case for the web apps I work on). The general idea is to make the DB connection transparent, such that it connects the first time my script executes a query, and then it remains connected until the script termina...
Does Delphi call inherited on overridden procedures if there is no explicit call in the code ie (inherited;), I have the following structure (from super to sub class) TForm >> TBaseForm >> TAnyOtherForm All the forms in the project will be derived from TBaseForm, as this will have all the standard set-up and destructive parts that are ...
Does anyone know what the motivation was for having the reintroduce keyword in Delphi? If you have a child class that contains a function with the same name as a virtual function in the parent class and it is not declared with the override modifier then it is a compile error. Adding the reintroduce modifier in such situations fixes the...
My question is simple; is it possible to over object-orient your code? How much is too much? At what point are you giving up readability and maintainability for the sake of OO? I am a huge OO person but sometimes I wonder if I am over-complicating my code.... Thoughts? ...
So I'm refactoring my code to implement more OOP. I set up a class to hold page attributes. class PageAtrributes { private $db_connection; private $page_title; public function __construct($db_connection) { $this->db_connection = $db_connection; $this->page_title = ''; } public function get_page_title() { return $this->...
In what scenarios is it better to use a struct vs a class in C++? ...
To make a JavaScript class with a public method I'd do something like: function Restaurant() { } Restaurant.prototype.buy_food = function() { // something here } Restaurant.prototype.use_restroom = function() { // something here } That way users of my class can: var restaurant = new Restaurant(); restaurant.buy_food(); restau...
In effect, if I have a class c and instances of $c1 and $c2 which might have different private variable amounts but all their public methods return the same values I would like to be able to check that $c1 == $c2? Does anyone know an easy way to do this? ...
I would like to generate a list of differences between 2 instances of the the same object. Object in question: public class Step { [DataMember] public StepInstanceInfo InstanceInfo { get; set; } [DataMember] public Collection<string> AdHocRules { get; set; } [DataMember] public Collection<StepDoc> StepDocs ...
I have heard that the Liskov Substitution Principle (LSP) is a fundamental principle of object oriented design. What is it and what are some examples of its use? ...
When should I use an interface and when should I use a base class? Should it always be an interface if I don't want to actually define a base implementation of the methods? If I have a Dog and Cat class. Why would I want to implement IPet instead of PetBase? I can understand having interfaces for ISheds or IBarks (IMakesNoise?), becau...
I have a start of a webapp that I wrote without using the Object Oriented features of PHP. I don't really know if it is worth it to go back and rewrite the parts I have finished. Is object oriented PHP worth rewriting all or part of a decent working app? ...
Hi, I remember back when MS released a forum sample application, the design of the application was like this: /Classes/User.cs /Classes/Post.cs ... /Users.cs /Posts.cs So the classes folder had just the class i.e. properties and getters/setters. The Users.cs, Post.cs, etc. have the actual methods that access the Data Access Layer, so ...