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Questions tagged [downcast]

Downcasting permits an object of a superclass type to be treated as an object of any subclass type.

589 questions
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why the value of ' *ptr ' in the step 3 not equal 3 but 0?

I find that the value of '*ptr' in the steps:3 does not equal 3 #include using namespace std; int main(int arg, char* args[]) { int* ptr; int x = 4; float y = 3.142; cout << y << " " << &y << endl; //step:1 …
Mohamed
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Upcast non-generic ObjC Classes to parent class for Swift method parameter

I have some classes defined in Objective-C similar to this: @interface Type: NSObject { } @end @interface SubType1: Type { } @end @interface SubType2: Type { } @end @interface Parent : NSObject @property…
Bogdan
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Scala: downcasting throws java.lang.ClassCastException

Coming from a non-Java background to Scala has brought me a wide range of difficulties including this one. scala> class A defined class A scala> class B extends A defined class B scala> val a = new A a: A = A@2e893a4a scala> val b = new…
parsa
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Upcasting/Downcasting to handle mutliple derived classes by base class

Let's say I have a base class and multiple derived classes and I want to avoid having multiple variables/functions for every derived class type. The only way I found to realize this is using up-/downcasting. But especially downcasting is often…
Odysseus
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Can't add viewContoller to Tab Bar programmatically in the AppDelegate

I'm trying to add a viewController to the existing Tab Bar programmatically through didFinishLaunchWithOptions, but my code doesn't work, i can't downcast the rootViewController as UITabBarController. func application(_ application: UIApplication,…
Khuda
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Pointer Upcast and Downcast

Pointer Downcast int* ptrInt; char * ptrChar; void* ptrVoid; unsigned char indx; int sample = 0x12345678; ptrInt = &sample; ptrVoid = (void *)(ptrInt); ptrChar = (char *)(ptrVoid); /*manipulating ptrChar */ …
Amirah Reyna
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Downcasting with reinterpret_cast

I am a person, who loves to go deep into nitty-gritty details. This time I created really simple functionality, which I called "Scenario" (look under for code). First I will present to you my vision of it: struct ScenarioContext { virtual…
Black
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Cannot convert object of base instance to derived type (generics usage)

I have a generic version of an interval with start and end, and a concrete class that uses DateTime. The generic version defines an Empty value for convenience. The problem comes when I run the this code. It complaints in the only line of the Main…
SuperJMN
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draw uml class diagram with both super class object and subclass object being called in a third class

I have a Class A which is the super class of the class B (that is public class B extends A). Now I have a another class C, Class A is a instance variable in class C and class B is being downcasted from Class A and being assign to a local variable in…
Rui
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problem with a HashSet's Iterator

I'm trying to see if HashSet would be the solution for my next project so i'm doing some very easy test to check functionalities. I have a simple class Klant: public class Klant { private int klantNummer; public Klant(int nummer) { …
JBoy
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F# Downcasting arrays without reflection

I am working on a program where the user can send me all sort of objects at runtime, and I do not know their type in advance (at compile time). When the object can be down-cast to an (F#) array, of any element type, I would like to perform some…
Janthelme
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What does upcasting and downcasting look at? (Object type or Reference type)

I am a beginner and I am confused between these two examples. So sorry if I ask something that has already be answered. I don't know how to search for this issue. Let's say I have class Person and class Student. Student extends Person. So when I…
Stefan Jankovic
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How to avoid downcasting when using a list of subclass items in Java

I have an abstract class A and classes B and C. Classes B and C extend A. I need to hold B and C in the list together, say List. However, B and C have unique methods, so not all items in List can be used to invoke certain methods unless I am…
Michael Michael Michael
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JPA: select in polymorphic entities with JPQL, eclipselink and joined inheritance using multiple downcast

I'm having an interesting exercise trying to select multiple derived entities using a single JPQL query while with eclipselink 2.7.6. The polymorphism is implemented using joined inheritance. The entities diagram and the java classes are as…
el.nicko
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Java ArrayList Downcasting

So I've been working in a project in which I need to have a list to be filled with its new child class objects. I've made it with traditional method which one ArrayList will be filled with a type of child Class. But to make the code shorter and…
Dean Debrio
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