what are the use of interfaces and diffrences with respect to interfaces
What are the major advantages of interfaces in designing application and the differences with respect to inheritance. can any body provide me with the brief example. ...
inheritance
"import" a definition of a function from a base class to implement abstract interface (multiple inheritance in C++)
Say we have a class inheriting from two base classes (multiple inheritance). Base class A is abstract, declaring a pure virtual function foo, the other base class B declares and implements a function foo of the very same signature. struct A { virtual void foo(int i) = 0; }; struct B { virtual void foo(int i) {} }; struct C : publi...
Are accessors in Python ever justified?
I realize that in most cases, it's preferred in Python to just access attributes directly, since there's no real concept of encapsulation like there is in Java and the like. However, I'm wondering if there aren't any exceptions, particularly with abstract classes that have disparate implementations. Let's say I'm writing a bunch of abst...
What are the disadvantages of using inheritance as a way of reusing code?
What are the disadvantages of using inheritance as a way of reusing code? ...
need multiple inheritance in Objective C
I want to implement a movable UIView class (view moves when you touch on it and move your finger), e.g.: @interface MovableView : UIView { some members; } -touchesBegan; -touchesMoved; @end How can I apply this code to UILabel, UIButton etc without multiple inheritance? In C++, I'd do it like this (with UIView as a virtual base to ...
Containing hidden "objects" in ListviewItem, with inheritance?
Hello! I have a listview control, and it's data refreshing continously. I'd like to 'put' an XElement into a row, so I if e.g. double-click on the row, the double-click would call a method, with the 'hidden' xelement parameters. I hope I started to solve it, the debugger doesn't show any errors, but I don't know how to reach the XEleme...
Django subclasses having unique IDs
Assuming I have an abstract class ("AbstractClass") and two subclasses ("Subclass1" and "Subclass2"), two separate database tables will be created to hold instances of Subclass1 and Subclass2. These database tables currently number normally, from 1 upwards. Is there a way to ensure the IDs of all implementing subclasses are unique betwe...
Attribute Inheritence and Reflection
Hello All, I have created a custom Attribute to decorate a number of classes that I want to query for at runtime: [AttributeUsage(AttributeTargets.Class, AllowMultiple=false, Inherited=true)] public class ExampleAttribute : Attribute { public ExampleAttribute(string name) { this.Name = name; } public string N...
Java Interface Implementation Problem
Hello everyone. I have a little problem. Class ll: interface jj{ public class ll implements gg{ public static String j ="C:\\"; //some code here } } Class ggg: interface gg{ public class ggg extends JFrame implements jj{ //bunch of code + a textfield textField = new JTextField(); textFi...
How is Java inheritance being used to enforce program requirements?
I was looking at a blog about good API design link text In one of the example sections titled 'Reinventing the Socket', it showed a design of how to enforce certain rules and prerequisite on the client code that uses it. eg. the client must call bind() before it can call connect(), and it must be connected before it's allowed to send() ...
Interacting classes - organizing code
Hello to everyone! I have some problem with organizing classes properly. Suppose, I have some class ABase. When I want to create some different (more particular) abstraction of this class (denote it AParticular), I can use inheritance or just composition. Then it is easy to treat AParticular as ABase: in case of inheritance it is made a...
Inheritance, Calling base class ctors
class Base{ public: Base(int val):_id(val){}; int _id; }; class Derived : Base { public: Derived(int val):Base(_id+val){}; }; int main(){ Derived d(60); } why doesn't this give an error? Base class is still not constructed but I'm able to use '_id'? thanks ...
Can I change the super of a class?
Hi, Is it somehow possible to choose the super of a class (preferably in the alloc or init method) so my class inherits from something else? ...
When to implement an interface and when to extend a superclass?
I've been reading a lot about interfaces and class inheritance in Java, and I know how to do both and I think I have a good feel for both. But it seems that nobody ever really compares the two side by side and explains when and why you would want to use one or the other. I have not found a lot of times when implementing an interface woul...
How to stop css inheritance in sub unorder list
Hi guys I am trying to setup a menu with sub menu that contains ul. My question is how to remove the sub ul menu background image that inherits from the menu ul. I appreciate any help. Thanks a lot! my html <ul id="menuBar"> <li id="test1">test1</li> <li id="test2"><a href="#">Pro1</a> <div class="subMenu"> <ul> ...
Should I be using inheritance?
This is more of a subjective question, so I'm going to preemptively mark it as community wiki. Basically, I've found that in most of my code, there are many classes, many of which use each other, but few of which are directly related to each other. I look back at my college days, and think of the traditional class Cat : Animal type exam...
A (somewhat obscure) Javascript inheritance question
I have been experimenting with a design pattern in Javascript that would allow me to have what appears to be singleton functions that can be overridden by instance functions. Here's a brief example: Date.tomorrow = function () { return Date.today().add(1).days(); } (function(p) { p.tomorrow = function() { var date = this.clon...
Is there a way to truly extend a Flex component?
I need to create an extension of a Flex component, which (obviously) means that the new component should be able to be used whenever the parent is used. But I don't see the way to do it, Flex offers two ways of extending a component, by defining an AS class extending the parent or by creating an MXML file that uses the parent component a...
What does inheritance in UML do with your ERD?
Hi, I created a class diagram for a system and now I have to model it into a real system. This means converting it to a database. Now there is a base class which has just a few attributes, but there are many classes that inherit from it. Now my checklist for converting says I have to create a table for every class. I don't know how to...
Can derived class use friend function of the basis class?
Hello, If I have some class Basis, and derived from it Derived, inside basis I have friend function friend int operator!=(const Basis&, const Basis&) Inside derived class I don't have such function So my question is if I have inside my main If( derived1 != derived2 ) ... why does it work? i don't have any constructor for casting f...