Why wouldn't DoesntWork() work below? The error is: Cannot implicitly convert type 'List' to 'IEnumerable'. An explicit conversion exists (are you missing a cast?). I know this is something about generic/templates I'm not getting, but List is IEnumerable and Implementer is an IInterface. I don't see why this needs to be casted (or if ...
My question is not easy to explain using words, fortunately it's not too difficult to demonstrate. So, bear with me: public interface Command<R> { public R execute();//parameter R is the type of object that will be returned as the result of the execution of this command } public abstract class BasicCommand<R> implements Command<R> ...
I'm very confused with javascript methods defined in objects and the "this" keyword. In the below example, the toString() method is invoked when Mammal object instantiated: function Mammal(name){ this.name=name; this.toString = function(){ return '[Mammal "'+this.name+'"]'; } } var someAnimal = new Mammal('Mr. Biggles'); alert...
Please explain me below situation What would be the output? interface A{} class B implements A{} class C extends B{} class D extends C{} class E extends D{ public static void main(String args[]){ C c = new C(); B b = c; A a = (E)c; a = (B)c; c = (C)(B)c; } } ...
#include<stdio.h> class A {public: int a; }; class B: public A {private: int a;}; int main(){ B b; printf("%d", b.a); return 0; } #include<stdio.h> class A {public: int a; }; class B: private A {}; int main(){ B b; printf("%d", b.a); return 0; } I ask because I get different errors: error: 'int B::a' ...
Can you explain why this is not allowed, #include <stdio.h> class B { private: int a; public: int a; }; int main() { return 0; } while this is? #include <stdio.h> class A { public: int a; }; class B : public A{ private: int a; }; int main() { return 0; } In both the cases, we have one public and one pri...
I'm trying to use inheritance among classes defined inside a class template (inner classes). However, the compiler (GCC) is refusing to give me access to public members in the base class. Example code: template <int D> struct Space { struct Plane { Plane(Space& b); virtual int& at(int y, int z) = 0; Space& s...
Does anyone have experience reducing template code bloat using inheritance? i hesitate rewriting our containers this way: class vectorBase { public: int size(); void clear(); int m_size; void *m_rawData; //.... }; template< typename T > class vector : public vectorBase { void push_back( const T& ); //......
I have a simple has_many/belongs_to relationship between Report and Chart. The issue I'm having is that my Chart model is a parent that has children. So in my Report model I have class Report < ActiveRecord::Base has_many :charts end And my Chart model is a parent, where Pie, Line, Bar all inherit from Chart. I'm not sure where the...
I'm using model inheritance to manage a multiple models queryset: from django.db import models from django.contrib.sites.models import Site from django.contrib.auth.models import User from imagekit.models import ImageModel import datetime class Entry(models.Model): date_pub = models.DateTimeField(default=datetime.datetime.now) ...
It's said that composition is preferred over inheritance. Every single open source GUI toolkit however uses inheritance for the drawn widgets (windows, labels, frames, buttons, etc). I checked Qt, wxWidgets, and GTK+. Is there an example of a GUI toolkit (written in any language) that uses composition instead of inheritance to separat...
Sorry about the strange title. I really have no idea how to express it any better... I get an error on the following snippet. I use the class Dummy everywhere. Doesn't the compiler understand the constraint I've added on DummyImplBase? Is this a compiler bug as it works if I use Dummy directly instead of setting it as a constraint? Err...
I was told that static methods in java didn't have Inheritance but when I try the following test package test1; public class Main { /** * @param args the command line arguments */ public static void main(String[] args) { TB.ttt(); TB.ttt2(); } } package test1; public class TA { static publi...
I have a situation where i have a class class Foo { Foo Bar() { return new Foo(); } } Now i wan tot create an interface for it class IFoo { ??? Bar(); } What should be in place of the question marks? Each class should return it's own type, not Foo. The solutions below work but do not looks clean. I don't ...
can somebody please help me with an error conversion from `A' to non-scalar type `B' requested I have class A and derived from it B, but I have problems with these rows: A a(1); A *pb = new B(a); B b = *pb; //here I have an error thanks in advance for any help class A { protected: int player; public: A(int initPlayer =...
I am trying to stop a class from being able to convert its 'this' pointer into a pointer of one of its interfaces. I do this by using private inheritance via a middle proxy class. The problem is that I find private inheritance makes all public static members and types of the base class inaccessible to all classes under the inheriting cla...
I received homework to make program without casting using constructors so this is my code, I have two classes: class Base { protected: int var; public: Base(int var = 0); Base(const Base&); Base& operator=(const Base&); virtual ~Base(){}; virtual void foo(); void foo() const; operator int(); }; class Der...
Suppose I have a bunch of fruit: class Fruit { ... }; class Apple : public Fruit { ... }; class Orange: public Fruit { ... }; And some polymorphic functions that operate on said fruit: void Eat(Fruit* f, Pesticide* p) { ... } void Eat(Apple* f, Pesticide* p) { ingest(f,p); } void Eat(Orange* f, Pesticide* p) { peel(f,p); ingest...
Let's say I have a base class Animal from which a class Cow inherits, and a Barn class containing an Animal vector, and let's say the Animal class has a virtual function scream(), which Cow overrides. With the following code: Animal.h #ifndef _ANIMAL_H #define _ANIMAL_H #include <iostream> using namespace std; class Animal { public: ...
Hello All.... I am just refreshing the oops features of the java. So, I have a little confusion regarding inheritance concept. For that I have a following sample code : class Super{ int index = 5; public void printVal(){ System.out.println("Super"); } } class Sub extends Super{ int index = 2; public void pr...