Questions tagged [upcasting]
Upcasting permits an object of a subclass type to be treated as an object of any superclass type.
upcasting
244
questions
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Is C# element inside Tuple cannot be upcasted? [duplicate]
I'm encountering a compilation error in C# .NET 8.0 when trying to pass a Dictionary with a tuple as its key to a method. The tuple consists of a base class and another class, but when I try to use a ...
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1
answer
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views
Upcasting trait in an option field
I am just learning Rust and have some issues with upcasting a trait ref inside an option. I want to pass it as ref to reduce the overhead.
The basic idea is as follows:
I have some objects (children) ...
- 31
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Up Casting Using References Instead Of Pointers
I wonder if the following up-casting is valid? And if yes, is it possible to down-cast in the same way?
class A {
public:
A(){ cout << "A constructor\n";};
A(const A& a){ ...
- 81
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3
answers
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Can someone please explain this Java upcasting behavior I am little confused?
In the code given below when we are trying to initiate object of type A by calling the constructor of a child class when we print x.i java refers to the parent class attribute and why when called ...
-2
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1
answer
202
views
Upcasting and downcasting in Java and polymorphism
I'm confused why or when to use downcasting and upcasting and polymorphism.
Am I correct or wrong?
If we say this Gift gift = new Pen(); not only can we leverage the use of polymorphism (if subclass ...
0
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1
answer
56
views
Clarifying some relationships between types, upcasting, and classes/interfaces [duplicate]
Everything occurs in Java. I'm not sure to what extent the programming language affects my questions, and I would be interested to know.
Suppose I have a class Animal, and a subclass which extends ...
- 111
0
votes
2
answers
54
views
Populating a list from a class with objects from other classes
I am having the next code arhitecture:
class candybox with arguments flavor and origin which is the parent class for classes: Lindt, Baravelli and ChocoAmor which will have as a plus arguments: ...
- 1
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2
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58
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Will upcasting classes affect the method call? Why? Security issues? [duplicate]
Let's have the specified code:
class Foo {
public void doSomething(){
System.out.println("Foo");
}
}
class Bar extends Foo{
@Override
public void doSomething(){
...
- 106
0
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2
answers
140
views
In scala 3, is it possible to make covariant/contravariant type constructor to honour coercive subtyping?
This is a simple example:
object CoerciveCovariance {
trait Cov[+T]
def cast[A, B](v: Cov[A])(
implicit
ev: A <:< B
) = {
v: Cov[B]
}
}
It doesn't compile:
...
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0
votes
1
answer
95
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Using protected method of the parent class in another package
I have Tadpole class that extends Frog, as follows:
1: package animal;
2: public class Frog {
3: protected void ribbit() { }
4: void jump() { }
5: }
1: package other;
2: import animal.*;
3: ...
- 51
0
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2
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77
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Can't cast from a child ref to a parent ref in C#. Why not? [duplicate]
I am new to using C#. I am most familiar with C++ and Java when it comes to Object-Oriented Programming and polymorphism. Can someone tell me why this upcast does not work in C#, and what I can do to ...
- 201
1
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0
answers
82
views
Upcasting a widget
In a Rust GTK4 application, an event handler needs to send a message to its root, which is a subclass of ApplicationWindow. I can get the root in the handler by "button.property("root")....
- 698
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0
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Java upcasting and downcasting problem as follow [duplicate]
I got confused, as the answer suggested option A.
Shouldn't aVehicle bound be viewed as a Vehicle object since the first line operated upcasting?
The question as follow:
Consider the following code ...
- 11
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1
answer
70
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Why java upcasting causes overwritten girl method to be called? [closed]
I’m trying to understand upcasting with Java. I just created two classes Mom and Girl, with each having their own constructor (constructors have no parameters).
If I understand, Mom mom = new Girl() ...
- 65
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1
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325
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Java accesing properties with same name in both classes
I have 2 classes, A and B which B inherits from A.
Both classes have a property of type int called w.
In class A w is public and in class B w is private.
I made an object of type A using B constructor ...
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