Say we have: Class Base { virtual void f(){g();}; virtual void g(){//Do some Base related code;} }; Class Derived : public Base { virtual void f(){Base::f();}; virtual void g(){//Do some Derived related code}; }; int main() { Base *pBase = new Derived; pBase->f(); return 0; } Which g() will be c...
I've looked at other definitions and explanations and none of them satisfy me. I want to see if anybody can define polymorphism in at most two sentences without using any code or examples. I don't want to hear 'So you have a person/car/can opener...' or how the word is derived (nobody is impressed that you know what poly and morph means)...
I am working on a Django application which contains an Offer model. An Offer instance contains the pricing conditions and points to a product definition. The product model is actually a hierarchy (I have a Television model, a Camcorder model, etc.). So I would like the Offer model to contain a polymorphic (or "generic") association to...
I'm writing a simplistic game to learn get some more C++ experience, and I have an idea where I feel polymorphism almost works, but doesn't. In this game, the Party moves fairly linearly through a Map, but can occasionally encounter a Fork in the road. A fork is (basically) an std::vector<location*>.Originally I was going to code somethi...
I have a question on C++ double dispatch. In the code below, I want the results from the second set to match the results from the first set. I don't know the actual type (unless I try dynamic_cast) but I do know that the object inherited from the BaseClass type. What is the most efficient (performance-wise) way to accomplish this? Aft...
typedef void (FunctionSet::* Function)(); class MyFunctionSet : public FunctionSet { protected: void addFunctions() { addFunction(Function(&MyFunctionSet::function1)); } void function1() { // Do something. } }; The addFunction method adds the function to a list in the base class, which can then be en...
I am learning to use polymorphism in C#, but cannot figure out this one. I'm trying to write a class that allows me to get a filtered list of files from a repository. The repository could be a file system folder or the embedded resources in an arbitrary already-loaded assembly (but it is not the one currently executing). Any suggestio...
I've got a polymorphic array of objects which implement two (informal) interfaces. I want to be able to differentiate them with reflection along the lines of: if (hasattr(obj, 'some_method')) { # `some_method` is only implemented by one interface. # Now I can use the appropriate dispatch semantics. } else { # This must be th...
When using the std::for_each, class A; vector<A*> VectorOfAPointers; std::for_each(VectorOfAPointers.begin(), VectorOfAPointers.end(), std::mem_fun(&A::foo)); If we have classes inheriting from A and implementing foo(), and we hold a vector of pointers to A, is there any way to call a polymorphic call on foo(), rather then explicitl...
Suppose we have the following class hierarchy: class Base { ... }; class Derived1 : public Base { ... }; class Derived2 : public Base { ... }; Given a Base* which could point to either a Derived1 or Derived2 object how can I make a copy of the actual object given that it's concrete type is unknown. I thought of defining ...
I have some logic, which defines and uses some user-defined types, like these: class Word { System.Drawing.Font font; //a System type string text; } class Canvass { System.Drawing.Graphics graphics; //another, related System type ... and other data members ... //a method whose implementation combines the two System types in...
Hi I'm working on a class that inherits from another class, but I'm getting a compiler error saying "Cannot find symbol constructor Account()". Basically what I'm trying to do is make a class InvestmentAccount which extends from Account - Account is meant to hold a balance with methods for withdrawing/depositing money and InvestmentAcco...
How can polymorphism replace an if-else statement or Switch inside of a loop? In particular can it always replace an if-else? Most of the if-thens I use inside of loops are arithmetic comparisons. This question is spawned from this question. int x; int y; int z; while (x > y) { if (x < z) { x = z; } } How woul...
Is there a way to write OO-like code in the C programming language? See also: http://stackoverflow.com/questions/351733/can-you-write-object-oriented-code-in-c http://stackoverflow.com/questions/415452/object-orientation-in-c Found by searching on "[c] oo". ...
I'm a big fan of TDD and use it for the vast majority of my development these days. One situation I run into somewhat frequently, though, and have never found what I thought was a "good" answer for, is something like the following (contrived) example. Suppose I have an interface, like this (writing in Java, but really, this applies to ...
I ended up with something like the following code in a project I'm working on. I thought it was really odd that I was allowed to do it, but now I'm starting wonder what is most likely an architectural gaff on my part led me to this. My questions to you are: What exactly is this called? What are some real world uses of this? Why would...
Is it possible to do something like this? class A { public virtual string prop { get { return "A"; } } } class B: A { private string X; public override string prop { get { return X; } set { X = value; } ...
I use SWIG to wrap a Ruby script around a C++ library. In Ruby, I can inherit from a C++ class, but I cannot pass the resulting pointer to a C++ function in a polymorphic way. Here is a concrete example. The SWIG interface file defines base class Animal with virtual function sound(): [animals.i] %module(directors="1") animals %{ #i...
If I have a code like this: struct A { virtual void f(int) {} virtual void f(void*) {} }; struct B : public A { void f(int) {} }; struct C : public B { void f(void*) {} }; int main() { C c; c.f(1); return 0; } I get an error that says that I am trying to do an invalid conversion from int to void*. Why can't compiler...
I am building an AI for an RTS game. (For the Spring RTS engine, if anyone is interested.) The way I have set it up it consists mainly of a collection of Components that communicate by means of fired Events. Every component has a method handleEvent(Event) that receives events fired by the other components. Event is an interface. A hiera...