Downcasting permits an object of a superclass type to be treated as an object of any subclass type.
Questions tagged [downcast]
589 questions
0
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1 answer
Can I Initialize a derived class reference with a base class reference to derived class instance?
I have something like the following:
class A { ... };
class B : public A { ... };
// ...
B b;
const A& aref(b);
// ...
const B& bref(aref);
and when I compile, I get:
no suitable user-defined conversion from "const A" to "const B" exists
Now,…
einpoklum
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ostream to ostringstream(downcasting) in C++ with Qt & MVC
I need to convert a ostream's object in a ostringstream's object.
This is the code:
//gerarchia_view.h
class bagaglio_view{
private:
std::ostream& os;
std::string data;
public:
bagaglio_view();
std::string print_bagaglio(const…
BottCode
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3 answers
C# How to go from base class to derived one and not violate encapsulation
The question of downcasting has been raised on SO before, but I couldn't find any explanation on how to avoid it properly.
Consider this hierarchy, for example.
abstract class NetworkDevice
{
//some common fields & properties
}
class Router :…
Korli
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Unable to cast object of type 'Parent' to type 'Child'
I was trying to cast my parent into my child (aka Down casting). Below is the example for the same:
public class Parent
{
public void ParentMethod()
{
Console.WriteLine("In Parent Method");
}
}
public class Child : Parent
{
…
HarshSharma
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0
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3 answers
Swift function overriding Objective-C method
I have an Objective-C method (declared in the class named "BaseViewModel" of my old framework) that is :
-(void) updateFromManagedObject:(__kindof NSManagedObject *)entity;
I want to use it in mutiple Swift classes. Each Swift class will use a…
QLag
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2 answers
"downcast from CLplacemark? to Clplacemark only unwraps optional"(swift2)
how to fix this error :
"downcast from CLplacemark? to Clplacemark only unwraps optional"
so i use this code :
if let p = CLPlacemark(placemark: placemarks.first as? CLPlacemark){}
and change placemarks[0] array but not work
and my code is :…
user1707895
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0
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3 answers
How to downcast UIViewController in Swift
I have several view controllers inherited from UIViewController. The views are embedded in Tab bar controller. I implement a custom view transition controller so that view can be switched when I tap on tabbar item. Is it possible that I can know…
thsieh
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0
votes
1 answer
Declaring first, downcasting later
Say I have BaseClass, DerivedClassOne, DerivedClassTwo, a magical factory method giveMeAnObjectOfType(type: String) -> BaseClass, and the following code
func myBeautifulFunction(index: Int) -> BaseClass {
let type : String =…
Morpheu5
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How do I downcast a class to its base type to set values using Activator.CreateInstance?
Given
//all types of T inherit class name of BaseClass...
public void Test(Action CallBack){
var obj = (T) Activator.CreateInstance();
//Debugger shows obj of proper type and shows its proper baseclass
//now I want to change the base…
JWP
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0
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2 answers
Can you downcast a NSIndexPath to NSInterger
I have a AVPlayer class that I'm using in a detail view that takes a indexPath of type Int.
I am getting the indexPath from the table view tableViewDidSelectAtIndexPath before sending it to the detail VC to use.
I tried to just simply downcast the…
user4671001
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0
votes
1 answer
Downcast from '[PFObject]?' to '[PFObject]' only unwraps optionals
I am saving a parse query to a array but i ket the following error on if let objects = objects as? [PFObject]
And the following error happens Downcast from '[PFObject]?' to '[PFObject]' only unwraps optionals.
any one know how to solve this?
func…
user4174219
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0
votes
1 answer
Can not cast from source type to destination type
I am writing a game in Unity, and I am trying to use polymorphism to access 2 subclasses but keep getting an error:
Can not cast from source type to destination type
I have a serialized list of Places, and I am trying to downcast to a Property,…
Celestrial
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votes
2 answers
swift variable type won't change after downcast if the variable has been declared?
I intended to downcast a UITableViewCell to different subclasses based on which section it is in.
Suppose a subclass of UITableViewCell is CellOne and it has a var nameLabel. In one case, I downcast (as!) the UITableViewCell returned by…
ninikikki
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votes
1 answer
Same multiple downcasts in equals; will they be optimised?
I tend to write my equals method in Java as a one liner...
class Test {
private String a = "";
private Integer b = Integer.MIN_VALUE;
private Long c = Long.MIN_VALUE;
public Test(final String a, final Integer b, final Long c) {
…
Jagger
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0
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Coredata downcasting issue
I've the following code which is for editing my contact, but somehow I'm receiving this error: NSString is not a subclass of category. This is my code
func editContact() {
let index = pickerView.selectedRowInComponent(0)
let…
congolese developper
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