Say I have the folowing code: class Class1(object): def __init__(self): self.my_attr = 1 self.my_other_attr = 2 class Class2(Class1): def __init__(self): super(Class1,self).__init__() Why does Class2 not inherit the attributes of Class1? ...
(This question should probably be answered with a reference to Stroustrup.) It seems extremely useful to be able to request a pointer to the most derived class, as in the following: class Base { ... }; class DerivedA { ... }; class DerivedB { ... }; class Processor { public: void Do(Base* b) {...} void Do(DerivedA* d) {...} voi...
I want to extend the System.Web.UI.Page-class with some extra stuff. In the ctor I need the value of a session-variable. The problem is that the Session-object is null... public class ExtendedPage : System.Web.UI.Page { protected foo; public ExtendedPage() { this.foo = (int)HttpContext.Current.Session["foo"]; // NullR...
I am implementing a single table inheritance inside Rails. Here is the corresponding migration: class CreateA < ActiveRecord::Migration def self.up create_table :a do |t| t.string :type end end Class B inherits from A: class B < A end Now, it's easy to get all instances of class B: B.find(:all) or A.find_all_by_t...
Hi All, I have some classes inherit from existing Windows Controls like TextBox and DateTimePicker, ..etc I want to add custom functionalities for these classes like (Read, Alert, ...etc) these added functionalities are the same in all these classes The problem is: these classes inherited from difference parents so I can't put my adde...
I have an generic math-method, that operates under a set of functions (with a lot of variables and states, so it can't be static). I've implemented method in parent class and I want to declare a different set of functions in every child-class. I've try to do something like this: class A { public: typedef int (A::*func)(); func *...
I want to initialize constant in child-class, instead of base class. And use it to get rid of dynamic memory allocation (I know array sizes already, and there will be a few child-classes with different constants). So I try: class A { public: const int x; A() : x(0) {} A(int x) : x(x) {} void f() { double y[this-...
How do I make a class whose interface matches double, but whose templated types do not dynamic cast to double? The reason is that I have a run-time type system, and I want to be able to have a type that works just like double: template<int min_value, int max_value> class BoundedDouble: public double {}; And then use template speciali...
I have a base class called Element, a derived class called Vector, and I'm trying to redefine two virtual functions from Element in Vector. //element.h template <class T> class Element { public: Element(); virtual Element& plus(const Element&); virtual Element& minus(const Element&); }; and in another file //Vector.h #include "Eleme...
Howdy, I have got the following file heirarchy: project other stuff templates images images for site app1 templates for app1 registration login template base.html (base for entire site) style.css (for base.html) In the login template, I am extending 'base.html.' 'base.htm...
public class B { static int i =1; public static int multiply(int a,int b) { return i; } public int multiply1(int a,int b) { return i; } public static void main(String args[]) { B b = new A(); System.out.println(b.multiply(5,2)); System.out.println(b.multipl...
I have a subclass and a superclass. However, only the fields of the superclass are needed to be persist. session.saveOrUpdate((Superclass) subclass); If I do the above, I will get the following exception. org.hibernate.MappingException: Unknown entity: test.Superclass at org.hibernate.impl.SessionFactoryImpl.getEntityPersister(Se...
Does anyone know of a good tutorial demonstrating inheritance in an entity framework model preferably where MySQL is the backend? ...
I've got a series of web actions I'm implementing in Seam to perform create, read, update, etc. operations. For my read/update/delete actions, I'd like to have individual action classes that all extend an abstract base class. I'd like to put the @Factory method in the abstract base class to retrieve the item that is to be acted upon. ...
Hi, i would like to get the type of the derived class from a static method of its base class. How can this be accomplished? Thanks! class BaseClass { static void Ping () { Type t = this.GetType(); // should be DerivedClass, but it is not possible with a static method } } class DerivedClass : BaseClass {} // somewhere in the...
I have commands classes that implement ICommand { Execute } interface. Several commands have duplicate pieces of code. I have several options how to DRY: Create static helper class(es) and move duplicate code there Create commands inheritance with protected helper methods What would you suggest and why? ADDED Thank you everyone w...
Hello, Suppose I have 3 classes as follows (as this is an example, it will not compile!): class Base { public: Base(){} virtual ~Base(){} virtual void DoSomething() = 0; virtual void DoSomethingElse() = 0; }; class Derived1 { public: Derived1(){} virtual ~Derived1(){} virtual void DoSomething(){ ... } virtual v...
My question is rather simple, but I am stuck. How can I choose the desired constructor from base class? // node.h #ifndef NODE_H #define NODE_H #include <vector> // definition of an exception-class class WrongBoundsException { }; class Node { public: ... Node(double, double, std::vector<double>&) throw (WrongBoun...
Hi. I am writing a project on Google App Engine, within it I have a number of abstract classes that I hope I will be able to use in my future projects, and a number of concrete classes inheriting from them. Among other abstract classes I have an abstract servlet that does user management, and I hava an abstract user. The AbstractUser h...
I am confused as to why the new operator isn't working as I expected it to. Note: All classes below are defined in the same namespace, and in the same file. This class allows you to prefix any content written to the console with some provided text. public class ConsoleWriter { private string prefix; public ConsoleWriter(strin...