inheritance

Struct inheritance in c++

can struct be inherited in C++ ? ...

What is the syntax to use C# generics as a constructor name?

I've got a number of classes that inherit from Item<T>. Each class has a Create() method that I would like to move up into Item<T>. Yet the following code gets the error "Cannot create an instance of the variable type 'T' because it does not have the new() constraint": T item = new T(loadCode); What is the correction syntax to do th...

Inheritance in a composite structure

Hello everybody, i have a problem related to the design of a composite structure. I have an Expression abstract class that describes a generic mathematical expression. The idea is that an expression can be an atomic expression (like "x" or "3") or some kind of aggregation of atomic expressions (like summatories, productories, exponentia...

Declaring Known Types for data contracts in different assemblies

I have a method in a WCF service which returns a complex type (myComplexResult), which includes as one of its members a List (Of Common.myBaseClass). I want this list to hold items which can variously be of type Foo.myClass1 and Bar.myClass2, both of which inherit from Common.myBaseClass. Note that all of these classes are defined in d...

C#: No implict conversion from Class<Child> to Class<Base>

Following snippet wouldn't compile. With following error: Cannot implicitly convert type 'Container<ChildClass>' to 'Container<BaseClass>' class BaseClass {} class ChildClass : BaseClass {} class Container<T> where T : BaseClass {} class Program { static void Main() { // why doesn't this work? Container<BaseClas...

How to copy an ancestor to a descendant

Let's say I have an animal and now I want to make it a dog. How do I go about doing this in java? Right now I have a constructor that looks like public Dog(Animal animal) { this.setProperty(animal.getProperty); ... } While this works, it's fragile. Any other suggestions? ...

PHP5 Classes: inheriting a composed class?

Hey all, I'm trying to get the following to work, but I'm at a loss... class Foo { public $somethingelse; function __construct() { echo 'I am Foo'; } function composition() { $this->somethingelse = } } class Bar extends Foo { function __construct() { echo 'I am Bar, my parent is Foo'; } } c...

Problem with Generic Inheritance (Open Construction)

Hi, I am facing this strange problem while working with Generic Base Classes. I am having three levels of base class hierarchy while the fourth level is the concrete class. Something as below. // Level 0 (Root Base Class) public abstract class BusinessDataControllerBase<BDA> : IBusinessDataController { protected BDA da; publ...

C# getting details from subclasses

Hello, I'm a complete newbie to C# so excuse me if this looks weird. I have an abstract class called vefHlutir namespace Klasasafn { public abstract class vefHlutur { public abstract List<String> columnNames(); public abstract List<String> toStringList(); } } //Here is an object that inherits from this ab...

Is it possible to use hard-coded values in a base constructor?

I need to inherit from a base class, one method of which has a constructor with 8 arguments. I won't ever need all 8 arguments, I only need one. However, I do need to implement that method. public MyClass : BaseClass { public class MyClass(string myArg):base(arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8) { // do ...

How can I access a static property in a subclass when the property is located in a base class?

Let's say I have: public class Fruit { public static List<String> Suppliers { get; protected set; } static Fruit() { Suppliers = new List<String>(); Suppliers.Add("Company A"); } } public class Banana : Fruit { static Banana() { Suppliers.Add("Company B"); } } If I just do this...

Are static members inherited? (C++)

When static members are inherited, are they static for the entire heirarchy, or just that class, ie: class SomeClass { public: SomeClass(){total++;} static int total; }; class SomeDerivedClass: public SomeClass { public: SomeDerivedClass(){total++;} }; int main() { SomeClass A; SomeClass B; SomeDerivedClass C; ...

How to declare two different static variables? (C++)

EDIT: declaring them private was a typo, I fixed it: Relating to another question, if I declared a static variable in a class, then derived a class from that, is there any way to declare the static variable as individual per each class. Ie: class A: { public: static int x; }; class B:A { public: const static int x; }; does that defi...

Is there a design pattern that addresses how to manage multiple similar objects?

I have multiple objects that inherit from a base class and am trying to decide how the user should edit them. There are many common fields and a few fields that only apply to each sub class. Is there a design pattern to address this? I was thinking I could have one web page for each one or I could have a single web page and show/hide th...

How can I create an object whose derived class is specified implicitly by the creation properties?

I'm looking for a pattern for the following. (I'm working in Perl, but I don't think the language matters particularly). With a parent class Foo, and children Bar, Baz, Bazza. One of the methods for constructing a Foo is by parsing a string, and part of that string will implicitly specify which class is to be created. So for example i...

How do I set up a static list of per-type/class metadata?

This is a follow up to this question... First, I have this: public class ListForType<T> { private Dictionary<Type, List<T>> listForType = new Dictionary<Type, List<T>>(); public void AddList(Type type, params T[] list) { AddListForType(type, list); AddListFromSuperiorTypes(); } public T[] ...

Is it ever valid to convert an object from a base class to a subclass

In my application at the moment I have (as in so many other applications) an entity called Contact, which represents any person. At its most basic level this is used to represent business contacts. However it can also be used to represent employees of the company. and there are also a couple of special types of employee (let say there is...

How is C++'s multiple inheritance implemented?

Single inheritance is easy to implement. For example, in C, the inheritance can be simulated as: struct Base { int a; } struct Descendant { Base parent; int b; } But with multiple inheritance, the compiler has to arrange multiple parents inside newly constructed class. How is it done? The problem I see arising is: should the parents ...

Is it possible to extend a class with only private constructors in Java?

For unit testing purposes I'm trying to write a mock object of a class with no constructors. Is this even possible in Java, of is the class simply not extensible? ...

C#: How to call a second-level base class method like base.base.GetHashCode()

class A { public override int GetHashCode() { return 1; } } class B : A { public override int GetHashCode() { return ((object)this).GetHashCode(); } } new B().GetHashCode() this overflows the stack. how can i call Object.GetHashCode from B....