I'm having an issue with inheritance between 2 classes and a single normal class. Here is an example of what I have: Abstract ClassA function get_name(); Abstract ClassB extends ClassA ClassC extends ClassB Now, when I create an object of ClassC, I can't access the get_name() function. I'm not sure what I'm doing wrong here. ...
Hi! I wish to say that a certain parametrized monad st works with a regular memory, but a subclass of my parametrized monad should impose an additional constraint on the type of memory. In code: class Memory m where ... class State st where unit :: Memory m => a -> st m m a bind :: (Memory m1, Memory m2, Memory m3) => st m1...
I'm doing this in the context of Android, but my problem is understanding Java. I'm somewhat new to both, so hopefully I'm using the correct terminology here. I've got a number of sub-classes inheriting/extending from my super class (an Android Activity extension) called SuperActivity. I've also defined another class type called Netwo...
I have two classes LightA and LightB. I have the source code of LightB but not that of LightA. I extended LightB with LightDimDip. ie LightDimDip:extends LightB. Now I need to apply DimDip feature to lightB also. Can any one suggest good OOP design. Once again I remind you people that I cannot modify LightA. ...
I know the title's a bit wordy, but I don't know how else to ask this question. This is basically the technique that I've been using to filter the types of objects you pass into an inherited class. Have a look at the code first and I'll explain more... public interface IProjectile {} public interface IPaintBall : IProjectile {} public i...
Is there a way to detect (for instance with compiler warning) if classes are declared friend but do not access private members, ie. when friendship is useless? ...
From MasterExam: Which statements are true? (Choose all that apply) A. is-a relationship always rely on inheritance B. is-a relationship always rely on instance variables C. is-a relationship always require at least two class types D. is-a relationship always rely on polymorphism E. is-a relationship are always...
Hello Every one. Here I can do conversion from emp class object to emp class object. But I can't do conversion from employee class object to emp class object - I have added comment where I am getting error - 'setEmpID' is not a member of 'employee'. what should I do to resolve this error ? ( I am just preparing for C++ exam & this is t...
I'm interested in subclassing the built-in int type in Python (I'm using v. 2.5), but having some trouble getting the initialization working. Here's some example code, which should be fairly obvious. class TestClass(int): def __init__(self): int.__init__(self, 5) However, when I try to use this I get: >>> a = TestClass()...
Hello, i have two tables in DB: Foo and Bar Using Entity Framework i want to create base entity which will contain properties which both tables have. For example Foo has columns Id,CreateDate,FooValue and Bar has Id,CreateDate,BarValue So BaseEntity should have Id and CreateDate properties Foo should inherit BaseEntity and have Foo...
This is a fairly lengthy (not overly complex) design question so please bear with me. I'm trying to implement a person/role management system with POJOs and JPA. I'm fairly new to ORM and this is mostly a mapping problem. I've got this working as POJOs and am comfortable with the caller-level API, but would now like to map it to a datab...
I have very little knowledge of generics other than how to 'use them'. In my app I have various ListView Activity that seem to share similar methods and variables and have the exact 'algorithm' in the sense that the steps performed are all very much the same. For example in my onCreate method I call a method to add a footer, start a pr...
Hi, I have mapped class in JPA. : @Entity @Inheritance(strategy = InheritanceType.JOINED) public class User { private Long id; private Long name; //getters and setters go here .... } I also have a subclass of this class, called Admin: @Entity public class Admin extends User { private String cridentials; //gett...
Why should virtual methods be explicitly overridden in C#? ...
I am writing the client side for a WCF service that supports both synchronous and asynchronous calls without having to implement 5-6 different methods in channel for each method in the contract. I have a base interface (IServiceClient) and a generic class based on this interface type (ServiceClient) as follows: public interface IServic...
I have the code as below. I have a abstract template class Foo and two subclasses (Foo1 and Foo2) which derive from instantiations of the template. I wish to use pointers in my program that can point to either objects of type Foo1 or Foo2, hence I created an interface IFoo. My problem is I'm not sure how to include functionB in the inte...
Hi, I would like to know the reason why this is first allowed in Java (or oops in general) I remember that the static methods are common for both parent and child class public class Redefine extends Parent{ public static void test () { } } class Parent{ public static void test () { } } Q1 : Since Overriding is ...
In django, I would like to reference the class whose method is being called, where the method itself is implemented in its abstract ancestor. class AbstractFather(models.Model): class Meta: abstract = True def my_method(self): # >>> Here <<< class Child(AbstractFather): pass I'm looking to do something lik...
I have a problem in a VB.Net class library which I have simplified greatly down to the following... Public MustInherit Class TargetBase End Class Public Class TargetOne Inherits TargetBase End Class Public Class TargetTwo Inherits TargetBase End Class Public Class TargetManager Public Sub UpdateTargets(ByVal Targets As L...
If i define class A { public int a; public float b; public A() { a = 10; } } class B extends A { public B() { a = 2; } } class C extends A { public C() { b = 2.0f; } } And in main public static void main(//...) { A a = new A(); B b = new B(); C c = new C(); a = b; //error? b = c; //this one too? } ...