C#•14mo ago

overriding methods

I have multiple questions:

1) What is the benefit of declaring a base method as

virtual

virtual

virtual

virtual before overriding it in an inheriting class? This is my understanding: it allows calling the override despite casting to the base class. Is this correct?

2) What is the difference between overriding a method, and hiding a method? As in, what does the

new

new

keyword do exactly?

becquerel•11/20/24, 10:26 PM

you have to declare methods as virtual (or abstract) to override them. you can't override them otherwise

becquerel•11/20/24, 10:26 PM

the

new

new

keyword changes nothing about the semantics of your program. it just stops the compiler from giving you a warning, because it now assumes you're using a method of the same name in the parent and child deliberately

DecoherenceOP•11/20/24, 10:29 PM

So what is the difference between these two?

Anton•11/20/24, 10:30 PM

1) if you don't, it'll call the method in the base class
2) you tell the compiler you mean the thing at 1) to happen

Anton•11/20/24, 10:30 PM

$code

AAnton $code

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Anton•11/20/24, 10:30 PM

put some code in the implementation

Anton•11/20/24, 10:30 PM

try calling it yourself

Anton•11/20/24, 10:31 PM

through the base class and through the child class

DecoherenceOP•11/20/24, 10:31 PM

Alright

Anton•11/20/24, 10:31 PM

I'd also recommend to make the base class abstract in such cases

DecoherenceOP•11/20/24, 10:32 PM

Anton•11/20/24, 10:32 PM

make stuff you inherit abstract if possible

Anton•11/20/24, 10:33 PM

make child classes sealed if you don't expect to inherit them further

DecoherenceOP•11/20/24, 10:33 PM

a virtual class being overriden prevents the base class default implementation from being ran, even if the instance's type is the parent class

Anton•11/20/24, 10:33 PM

but lastly, don't inherit if possible

DecoherenceOP•11/20/24, 10:34 PM

the CLR will infer the proper implementation

DecoherenceOP•11/20/24, 10:34 PM

this sounds useful if i have multiple classes inheriting from one class

DecoherenceOP•11/20/24, 10:34 PM

i could make uhhh

DecoherenceOP•11/20/24, 10:35 PM

List<baseclass> for example and ensure that the implemented .Display() will run and not the base's

AAnton but lastly, don't inherit if possible

DecoherenceOP•11/20/24, 10:37 PM

i want to nail the oop stuff first, i need to fully and properly grok every single thing about these concepts. once i do, i'll try to implement such advice

DDecoherence List<baseclass> for example and ensure that the implemented .Display() will run ...

Anton•11/20/24, 10:37 PM

that is how it's used

DecoherenceOP•11/20/24, 10:37 PM

im guessing it's the "composition over inheritence" argument, i hear you

Anton•11/20/24, 10:37 PM

it's not the best idea though

AAnton it's not the best idea though

DecoherenceOP•11/20/24, 10:37 PM

how would you do it?

DecoherenceOP•11/20/24, 10:38 PM

also, why an abstract method over a virtual one?

DDecoherence how would you do it?

Anton•11/20/24, 10:42 PM

It depends. Either make a separate system that decides what to call, or store an interface with the implementation somewhere, possible in a field or another list. I wouldn't want Person to both store data and declare virtual methods. It's harder to redefine things granularly like this, and reuse existing implementing instances. Some state may be shared, but you'd have to store it in the derived class anyway. It's less flexible and always produces kind of a mess

DecoherenceOP•11/20/24, 10:43 PM

abstract requires a lack of body

DDecoherence also, why an abstract method over a virtual one?

Anton•11/20/24, 10:43 PM

not method necessarily, class

DecoherenceOP•11/20/24, 10:43 PM

why an abstract class, so it doesnt get instanciated?

Anton•11/20/24, 10:43 PM

if you go abstract method, there's no benefit over using a base class over an interface

DecoherenceOP•11/20/24, 10:44 PM

semantics maybe?

DDecoherence why an abstract class, so it doesnt get instanciated?

Anton•11/20/24, 10:44 PM

so it's clear it's designed for inheritance

Anton•11/20/24, 10:44 PM

and shouldn't be used for other purposes

DecoherenceOP•11/20/24, 10:45 PM

so my last question is, what's the difference between abstract class and interface

Anton•11/20/24, 10:46 PM

the only instance where you'd want a base class, is when you wrap an interface implementation, calling into a virtual method, and have the child override that instead

Anton•11/20/24, 10:46 PM

in my experience that's like one of the very few use cases

DDecoherence so my last question is, what's the difference between abstract class and interfa...

Anton•11/20/24, 10:46 PM

abstract class can have fields

DecoherenceOP•11/20/24, 10:47 PM

interface can't have properties or fields?

Anton•11/20/24, 10:47 PM

fields

Anton•11/20/24, 10:47 PM

specifically

DecoherenceOP•11/20/24, 10:47 PM

thats weird

Anton•11/20/24, 10:47 PM

and you can only implement a single base class

DecoherenceOP•11/20/24, 10:47 PM

properties are backed by fields, so why can you have properties but not fields

Anton•11/20/24, 10:47 PM

but any number of interfaces

Anton•11/20/24, 10:48 PM

they're sort of virtual on interfaces

Anton•11/20/24, 10:48 PM

they're backed by fields when they're on a class

Anton•11/20/24, 10:49 PM

when they're on an interface, it just means get and set methods need to be present

Anton•11/20/24, 10:49 PM

it doesn't enforce the presence of a field

DecoherenceOP•11/20/24, 10:49 PM

overriding methods

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