polymorphism

Unable to find assembly, C#

So, here's the deal. I've got two ASP.NET applications, both of which use SQLServer Session State management. They also both use the same server. I've got a custom session class in an external DLL, which fully implements serialization, and which both applications have referenced. Each application, in turn, has a class which inherits from...

Obj-c method override/polymorphism problem

Ok, so I'm using Objective-C. Now, say I have: TopClass : NSObject - (int) getVal {return 1;} MidClass : TopClass - (int) getVal {return 2;} BotClass : MidClass - (int) getVal {return 3;} I then put objects of each type into an NSMutableArray and take one out. What I want to do is run the getVal func on the appropriate object type, ...

ChoiceFormat.setChoices confusion about format parameter type and documentation

From the java.text.ChoiceFormat API: setChoices(double[] limits, String[] formats): Set the choices to be used in formatting. Parameters: limits - contains [...] formats - are the formats you want to use for each limit. They can be either Format objects or Strings. When formatting with object Y, if the object is a ...

Why is the output like this?

class another { public void method(Object o) { System.out.println("This is in method which takes object"); } public void method(String s) { System.out.println("This is method which takes string"); } } public class NewClass { public static void main(String args[]) { another an = new another(); ...

Using Ruby on Rails, can a polymorphic database be created in a few steps (with polymorphic associations)?

I thought it could be created in a few steps but it can't yet: rails poly cd poly ruby script/generate scaffold animal name:string obj_type:string obj_id:integer rake:migrate ruby script/generate scaffold human name:string passportNumber:string rake:migrate ruby script/generate scaffold dog name:string registrationNumber:string rake:...

Recommendations for a C++ polymorphic, seekable, binary I/O interface

I've been using std::istream and ostream as a polymorphic interface for random-access binary I/O in C++, but it seems suboptimal in numerous ways: 64-bit seeks are non-portable and error-prone due to streampos/streamoff limitations; currently using boost/iostreams/positioning.hpp as a workaround, but it requires vigilance Missing opera...

Apples, oranges, and pointers to the most derived c++ class

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...

What are uses of polymorphic kinds?

Polymorphic kinds are an extension to Haskell's type system, supported by UHC, allowing data A x y = A (y x) to be typed (kinded?) as a -> (a -> *) -> *. What are they useful for? ...

c++ polymorphism and other function question

i have got this code: class father{ public: virtual void f() { cout<<1;} }; class son:public father{ public: void f() {cout<<2;} }; void test (father x){x.f();} int main(){ son s; test(s); } the question says: the output is '1', what is the rule about polymorphism that the programmer forgot and how can i fix it so...

How to get every virtual function index just as the compiler does?

Is there some plugin or tool which can read a .h file (or simply modify Intellisense itself) and spit out every function and it's virtual function table index? There's a pattern which I have yet to figure out having to do with polymorphism, and it gets 5x harder when you start to have 5 classes or more deriving from each other. No matter...

Can I pass a pointer to a superclass, but create a copy of the child?

I have a function that takes a pointer to a superclass and performs operations on it. However, at some point, the function must make a deep copy of the inputted object. Is there any way I can perform such a copy? It occurred to me to make the function a template function and simply have the user pass the type, but I hold out hope that ...

How to iterate through a sequence of bounded types with Boost.Variant

struct A { std::string get_string(); }; struct B { int value; }; typedef boost::variant<A,B> var_types; std::vector<var_types> v; A a; B b; v.push_back(a); v.push_back(b); How can I iterate iterate through the elements of v to get access to the a and b objects ? I'm able to do it with boost::get b...

Storing a derived object inside another object as a base pointer (C++)

So here's the deal: I have a concrete class Window, representing an operating system window which will be be used for drawing. Window can take on many types, such as fullscreen, fixed window, resizable window, borderless window etc. This is implemented using an interface IWindowType, in which the specific types derive from (classes are ...

Return-type polymorphism for pass-by-value

I'm not sure if the question title is accurate... Let me start by explaining my original simple scenario, and then move on to explain what would I like to do, but can't. Originally, I had something like: class Operand; Operand genOperandA() { ...; return Operand(); } Operand genOperandB() { ...; return Operand(); } ... // more operand...

Using java.lang.reflect.getMethod with polymorphic methods

Consider the following snippet: public class ReflectionTest { public static void main(String[] args) { ReflectionTest test = new ReflectionTest(); String object = new String("Hello!"); // 1. String is accepted as an Object test.print(object); // 2. The appropriate method is not found with ...

How to handle state transitions and yet replace "if" statements with polymorphic types?

Recently I was listening to a tech talk on clean coding. The speaker was a test engineer, who emphasized on avoiding the "if" statements in the code and use polymorphism as much as possible. Also he advocated against global states. I quite agree with him, yet i need a clarification on replacing the global state and "if" statement using ...

Overriding inherited types in Objective-C

This is probably a common Objective-C question reported by Java coders, but I don't know what to call it or how to search for the answer. Let's say I have a class and another class which extends it: AbstractModel @interface AbstractModel { } ModelImpl @interface ModelImpl : AbstractModel { } Separate from these, I have two more cl...

Using call_user_function to access parent method in PHP

Is there any way, in PHP, to call methods from a parent class using the arbitrary-argument call_user_func_array? Essentially, I want to write a little bit of boilerplate code that, while slightly less optimal, will let me invoke the parent to a method arbitrarily like this: function childFunction($arg1, $arg2, $arg3 = null) { // I d...

Nesting base classes in c#

I have 3 classes, two inherit from 1: public class Employee { private virtual double getBonus() { ... } private virtual double getSalary() { ... } } public class Nepotism : Employee { private double getBonus() { ... } } public class Volunteer : Employee { private double getSalary() { ... } } So the question is someti...

Polymorphic Enum in C++

I have these Enum declarations: enum MessageType{ REQ_LOGIN, REQ_GET_FIELD, RES_LOGIN, RES_GET_FIELD } enum Request{ REQ_LOGIN, REQ_GET_FIELD }; enum Respond{ RES_LOGIN, RES_GET_FIELD }; Obviously I'm repeating elements in Enum's. Is there any way to prevent this? EDIT: I'm using "MessageTy...