Unity default class and function is ref keyword used?

Unity Engine
1 
[System.Serializable]
public class SomeClass
{
    public int Someint;
    public string Somestr;
}

public class Test : MonoBehaviour
{
    // Start is called before the first frame update
    void Start()
    {
        SomeClass sc1 = new SomeClass();
        sc1.Someint = 2;
        Function(sc1);
        Debug.Log(sc1.Someint);
        Function2(ref sc1);
        Debug.Log(sc1.Someint);
    }
    public void Function(SomeClass sc)
    {
        sc.Someint = 4;
    }
    public void Function2(ref SomeClass sc)
    {
        sc.Someint = 4;
    }
}

The result is same 4, 4

I expected 2, 4

What is wrong? Unity default class, function is used [ ref ] keyword?

2

You’re not quite understanding what “ref” does. Since SomeClass is a reference type, you’ll always change the object sent in. ref gives you a reference to the variable sent in, so you could make that variable point at a different object.

If SomeClass was a struct, you’d get the behaviour you’re expecting.

3

OK, then how can I change SomeClass’s type?

4

When something doesn’t seem to work the way you’d expect it’s easy to think “oh, Unity does it differently”. Sometimes that’s true, but not for passing-by-ref. Unity does it the normal way. c# - Why use the 'ref' keyword when passing an object? - Stack Overflow has the best explanations I could find (in a 60 second search).

A thing to know is that C# is based on Java, and Java got rid of call-by-ref for being a combination of too complicated and rarely needed. Other newer languages followed suit. C# added it back, probably because C# likes having lots of features. Even worse, Unity only uses call-by-ref with structs. C# structs are even trickier (and another thing Java doesn’t have, since you don’t actually need them).

Fun story: a few years ago the microsoft web site said that classes were passed-by-reference. That’s completely wrong. My guess is that whoever wrote it realized there was no way to explain it correctly in a way that wouldn’t leave most people even more confused.

5

The hell are you on about?

Stucts are good. You need them. If every single vector operation in Unity involved visiting a random spot on the heap, stuff would just straight up be slower. Java’s adding in value types, exactly because they perform better in a ton of circumstances.

Pass by ref is not very hard to understand at all, and it enables you to write a ton of code in a much more consice way. If somebody doesn’t understand what it does, they don’t understand what a variable is, which means that they can’t really program.

The correct thing is that you “pass a reference”. It’s not very hard to explain. You could be pedantic about it, and say “pass the value of a reference”.

6

I mean, you just declare it as a struct in order for it to be a struct. But what are you trying to do?

7

ok, I see. I just curious if there were special type changing existed that I didn’t know.

8

I didn’t say structs are bad – I said they were extra tricky in C#. Everyone learns reference types first and uses classes everywhere. Then much later they learn structs are a weird type of class which can’t have references, may need this obscure thing called call-by-reference, and is only used in weird places to run a tad faster, like games.

If you look at C++ descriptions of structs, they’re the simplest thing in the world. But then you go to C# and they start: OK, you know how classes work, here’s how structs are different… .

This was in the section on call by reference, on the microsoft site. It said reference variables are passed-by-reference. I had to read it several times when I first saw it. I agree it’s not difficult to explain CBR in general. But in C# everyone has been passing reference variables and safely changing the contents for a long time before they see pass-by-ref. And you rarely need to pass a reference variable by reference (what a mouthful). In Unity I’ve only seen it in raycasts. In practice, it’s hard to explain to a typical C#-user.