I thought string was a reference type?!

[wyrd]

using System;

namespace ConsoleApplication3
{
class Class1
{
	[sTAThread]
	static void Main(string[] args)
	{
		new Class1();
	}

	public Class1() {
		string stuff = "yayaya";
		Console.WriteLine("before: " + stuff);
		changeString(stuff);
		Console.WriteLine("after: " + stuff);
		Console.Read();
	}

	private void changeString(string str) {
		str = "changed!";
		Console.WriteLine("function changed: " + str);
	}
}
}

 

This prints out the following;

 

before: yayaya

function changed: changed!

after: yayaya

 

Am I missing something?! I thought string was an object (reference type) while basic types like int, double, short, etc. and also enums and structures were value types.

 

:confused:

[divil]

Strings are indeed objects but they are immutable. Anything you do where it looks like you're doing something to a string, you're actually creating a new copy of it.

 

If you modified your above code to pass the string by reference instead of by value, you would get the result expected.

[wyrd]

Still that doesn't make sense to me. It should be automatically passed by reference, as it's an object. It's nothing more then a pointer to the first char in the char array which makes up the "string", and assigning it to a new "string" would do nothing more then point it to a new location.

 

*mumbles*

[wyrd]

I just read up on reference types and passing parameters in the MSDN library. It makes sense now according to the way .NET works. I guess I should get C++ off the brain.

 

Oh, and I learned about a new keyword I didn't know about before; out

 

:D

[John]

You do know also that all the built in data types are objects as well right, or was that what you found on MSDN?

[wyrd]

:rolleyes:

 

Yes, I know everything in .NET is an object. But I think you knew what I ment when I was talking about the string object (which is a reference type, not a value type)

 

My point was, passing reference types acts a tad differently then what I was thinking for some reason.

[John]

...But I think you knew what I ment when I was talking about the string object (which is a reference type, not a value type)...

No, I didn't. Sorry if it seemed that way. I just thought I would point it out in case you (or someone searching the forum in the future) didn't know.

[wyrd]

No, I didn't.

 

Oh. Well I have a habit of not using terms correctly, so I guess I should start paying more attention to what I'm typing.

[max1mum0v3rdr1v]

In case anyone is wondering, this is the correct way to get the above code working. Just need to assign to variable:

 

using System;

namespace ConsoleApplication3
{
   class Class1
   {
       [sTAThread]
       static void Main(string[] args)
       {
           new Class1();
       }

       public Class1() {
           string stuff = "yayaya";
           string newstuff = changeString(stuff);
           Console.WriteLine("before: " + stuff);
           Console.WriteLine("after: " + newstuff);
           Console.Read();
       }

       private string changeString(string str) {
           str = "changed!";
           Console.WriteLine("function changed: " + str);
           return str;
       }
   }
}

 

I only posted this for any n00bs out there that were curious as to how to make the above code function the way Wyrd seems to have expected it to.

 

--Sean