C#•2y ago

✅ stateful versus stateless methods?

Could someone please give me a simple example of these 2 methods as I don't really get what they do

115 Replies

So if you think about a method that is dependent on some value of a property of a class. Let's take a car for an example. You may have a public void Start() method. But this method may be dependent on the property public EngineType EngineType { get; set; }. This would be stateful because you can't perform that action without some knowledge about the object.

SoinagieOP•2y ago

sorry but I don't know what {get; set} do yet

Relevant•2y ago

But let's say you have a Math class, with a method public int Add(int a, int b). This method does not depend on any other properties of the object and can be performed without knowledge of anything outside of the method. Just ignore that part, then, it's just a property

SoinagieOP•2y ago

it needs a and b

Relevant•2y ago

But those are provided when the method is called. It doesn't depend on any current state of the Math object Let's say your Math class has a property name public int MyFavoriteNumber. The value of that property does not matter. It is not needed for the Add method

SoinagieOP•2y ago

how can something be an object and class anyway? class is a category of somethings, object is something like it doesn't make sense

Relevant•2y ago

a class is sort of like a set of rules for a type of thing. The object is the thing itself. Like the definition of a class might include something like a Color, Make, Model, and Year. That would be the class. The object would be the actual instance of Car. So like a Red 1999 Ford Escort

SoinagieOP•2y ago

so it does not depend on other properties of that class not object or is every class an object since it's an instance of itself?

Relevant•2y ago

no, a class is not an object Though when I said "properties of the object", I mean that the properties of an object can actually have values. Properties of a class are just definitions of properties, usually don't have values But that's kind of veering off course

SoinagieOP•2y ago

so stateful methods get other values out of their class or somewhere else, but not from themselfs stateless methods are 'self sufficient'

Relevant•2y ago

Stateful methods are dependent on the state of the object. Like my 1999 Ford Escort example. The Start() method might perform differently for that instance of Car versus a 2022 Tesla Model 3

SoinagieOP•2y ago

what objects? Im talking about methods

Relevant•2y ago

You're talking about methods dependent on object states

SoinagieOP•2y ago

I'm asking about stateless and stateful methods

Relevant•2y ago

Correct in other words, you're asking about methods that don't depend on object state versus methods that do depend on object state

SoinagieOP•2y ago

what objects? inside or outside of methods?

Relevant•2y ago

objects of the class that the method is contained in

Pobiega•2y ago

you can't randomly store state inside a method as such. you'll need either an object or a static variable to store that data in

SoinagieOP•2y ago

what state?

Pobiega•2y ago

ANY state

SoinagieOP•2y ago

methods are sets of actions, not states

Pobiega•2y ago

exactly

Relevant•2y ago

By state, we mean the state of the object. Or to word it differently, all of the values of all of the fields and properties at a given moment. That is it's state

Pobiega•2y ago

so you cant store state (aka data that lives longer than a single execution of a method) in them

SoinagieOP•2y ago

so object contains all of the values of their fields?

Pobiega•2y ago

we've been over this in your previous threads, yes

Relevant•2y ago

Properties more specifically, but yes

SoinagieOP•2y ago

I thought propeties were values?

Relevant•2y ago

properties hold values

SoinagieOP•2y ago

could you give me an example of stateless and stateful methods please?

Relevant•2y ago

properties and fields are both just variables, but named a little different to describe how/where they're used

SoinagieOP•2y ago

I thought they were the same both are stored in a class

Pobiega•2y ago

Consider these two classes and methods

public static class StatelessAdder
{
    public static int Add(int a, int b)
    {
        return a + b;
    }
}

public class StatefulAdder
{
    private int _value;

    public int Add(int a)
    {
        _value += a;
        return _value;
    }
}

public static class StatelessAdder
{
    public static int Add(int a, int b)
    {
        return a + b;
    }
}

public class StatefulAdder
{
    private int _value;

    public int Add(int a)
    {
        _value += a;
        return _value;
    }
}

the top one is entirely stateless. any two executions given the same values in will return the exact same value out

SoinagieOP•2y ago

Consider what?

Pobiega•2y ago

read the code?

SoinagieOP•2y ago

they're both classes

Pobiega•2y ago

try to see what it does? listen to our explanations?

Relevant•2y ago

Properties are generally public and have getter/setter. Fields are usually private. Both are defined at the class level, outside of methods

Pobiega•2y ago

Don't get caught up on the field vs property thing here @Soinagie , its not the important part

SoinagieOP•2y ago

what does this has to do with objects?

Pobiega•2y ago

I'm trying to answer your original question

Relevant•2y ago

Do you see why the 2nd one would be stateful?

SoinagieOP•2y ago

I think I already said I get that and Relevant confused me with this

Relevant•2y ago

Go back to that code example, and we'll get to objects. Do you understand why the 2nd one would be considered stateful?

Pobiega•2y ago

its (more or less) just a rephrase of your original question

SoinagieOP•2y ago

yeah bc it uses _value from field

Relevant•2y ago

Right So you could have two objects. One with a _value of 2, and the other with a _value of 4 And each object would get a different result from Add

SoinagieOP•2y ago

what? _value is a variable

Relevant•2y ago

correct

SoinagieOP•2y ago

then why did you call these objects?

Relevant•2y ago

I didn't

SoinagieOP•2y ago

Relevant•2y ago

When I say object, I mean an instance of the class

Pobiega•2y ago

because each object (instance of the class), would have its own _value

SoinagieOP•2y ago

but _value is a variable

Pobiega•2y ago

since _value belongs to the instance Are we seriously back to that discussion, again?

Relevant•2y ago

StatefulAdder adder1 = new StatefulAdder();
StatefulAdder adder2 = new StatefulAdder();

StatefulAdder adder1 = new StatefulAdder();
StatefulAdder adder2 = new StatefulAdder();

Pobiega•2y ago

Have you actually started visual studio at all since last we talked?

Relevant•2y ago

we have 2 StatefulAdder objects

SoinagieOP•2y ago

yeah

Relevant•2y ago

And they both have their own separate values of _value

SoinagieOP•2y ago

if you're just going to be mean feel free to leave

Relevant•2y ago

one of them might be 2 and the other might be 4 So if you do:

adder1.Add(2);
adder2.Add(2);

adder1.Add(2);
adder2.Add(2);

they would give you 2 different results

Pobiega•2y ago

Its a legitimate question to be honest. You need to actually write and run code to learn this.

SoinagieOP•2y ago

where? you didn't assign _value to them

Pobiega•2y ago

sure we did, thats done inside .Add

Relevant•2y ago

StatefulAdder adder1 = new StatefulAdder();
StatefulAdder adder2 = new StatefulAdder();

adder1.Add(2);
adder1.Add(2);

adder2.Add(2);

StatefulAdder adder1 = new StatefulAdder();
StatefulAdder adder2 = new StatefulAdder();

adder1.Add(2);
adder1.Add(2);

adder2.Add(2);

After this code executes, what would the values of _value be for each object? assuming _value starts at 0

SoinagieOP•2y ago

where is here _value?

Relevant•2y ago

_value as defined above is private. It can only be modified in the method

public class StatefulAdder
{
    private int _value;

    public int Add(int a)
    {
        _value += a;
        return _value;
    }
}

public class StatefulAdder
{
    private int _value;

    public int Add(int a)
    {
        _value += a;
        return _value;
    }
}

SoinagieOP•2y ago

but you didn't name it

Relevant•2y ago

didn't name what?

SoinagieOP•2y ago

how would code know to add specifically _value?

Relevant•2y ago

Look at the Add method _value += a; every time that method is called, it adds to _value

SoinagieOP•2y ago

and returns it where?

Relevant•2y ago

back to the caller, but that can be ignored for now here, we can just remove that to prevent confusion:

public class StatefulAdder
{
    private int _value;

    public void Add(int a)
    {
        _value += a;
    }
}

public class StatefulAdder
{
    private int _value;

    public void Add(int a)
    {
        _value += a;
    }
}

Pobiega•2y ago

return always returns to the caller btw there is no special case for that keyword

SoinagieOP•2y ago

what is StatefulAdder adder 1 = new StatefulAdder();? how can you add a whole class to a method? I mean I know it's an object

Relevant•2y ago

add a whole class to a method? I don't know what you mean by that StatefulAdder adder1 = new StatefulAdder(); This is just creating an object of a class

Pobiega•2y ago

its just an object reference

Relevant•2y ago

The variable name is adder1. It's type is StatefulAdder

SoinagieOP•2y ago

you're calling an object with adder1 and then adding to it?

Relevant•2y ago

creating an object named adder1 then calling it's Add method

Pobiega•2y ago

well in that first line of code its just creating the variable and giving it the value (being the object) the second line is what calls the Add method on it

SoinagieOP•2y ago

wait I thought adder1 was an object since you did New

Relevant•2y ago

it is, yes

SoinagieOP•2y ago

it is what?

Relevant•2y ago

an object

SoinagieOP•2y ago

but here you called it a variabe

Relevant•2y ago

yep it's both

SoinagieOP•2y ago

I can feel my brain melting...

Relevant•2y ago

an object is a variable

Pobiega•2y ago

ok this is now an exact repeat of the 1K+ posts "what is an object" thread.

Relevant•2y ago

I think there's probably exceptions to that, with dependency injection, etc, but that isn't the point right now

Pobiega•2y ago

Soinagie, please, for your own sake. Just start visual studio and start coding

SoinagieOP•2y ago

so stateful methods always call an object?

Pobiega•2y ago

write code, try to make it work, run it, test it

SoinagieOP•2y ago

and stateless don't?

Relevant•2y ago

It's challenging to understand state if you don't have a solid grasp of classes and objects

Pobiega•2y ago

most of the time... but of course there are exceptions... static variables exists.

SoinagieOP•2y ago

it was at the beggining of the tutorial

Relevant•2y ago

Yeah, stateless can be called without an object, but it can be stateless and also have an object stateful always has to have an object

SoinagieOP•2y ago

what good is it if I have no idea what anything does and why?

Pobiega•2y ago

Because you cant learn programming without actually coding most of your understanding will come from actually experimenting with the code not from reading

SoinagieOP•2y ago

and I can't start coding without knowing the basics

Pobiega•2y ago

oh you can. you have analysis paralysis at the moment, that much is clear

Relevant•2y ago

stateless vs stateful methods isn't a topic that matters when you're first starting

Pobiega•2y ago

seriously, just make an empty "hello world" console app project for now and add on that like, experiment with a single int variable, add to it, subtract from it... print it every now and then

artya•2y ago

What you're asking isn't really a basic

SoinagieOP•2y ago

it was in 3rd unit of $helloworld

MODiX•2y ago

Written interactive course https://learn.microsoft.com/en-us/users/dotnet/collections/yz26f8y64n7k07 Videos https://dotnet.microsoft.com/learn/videos

SoinagieOP•2y ago

in 5th module sorry for wasting your time

Pobiega•2y ago

go ahead and copy this code

public static class Program
{
    public static void Main()
    {
        var adder1 = new StatefulAdder();
        adder1.Add(10);
        
        var adder2 = new StatefulAdder();
        adder2.Add(10);
    }
}


public class StatefulAdder
{
    private int _value;

    public int Add(int a)
    {
        _value += a;
        return _value;
    }
}

public static class Program
{
    public static void Main()
    {
        var adder1 = new StatefulAdder();
        adder1.Add(10);
        
        var adder2 = new StatefulAdder();
        adder2.Add(10);
    }
}


public class StatefulAdder
{
    private int _value;

    public int Add(int a)
    {
        _value += a;
        return _value;
    }
}

try changing stuff around you can always copy paste again if you "break" it too much but seriously, "seeing how far things bend" is an excellent way to learn

SoinagieOP•2y ago

ok thank you and sorry again

Pobiega•2y ago

don't be sorry, be daring dont overthink stuff, just get your hands dirty

Relevant•2y ago

You'll get there, just don't be scared to break things 🙂 I mean, until you are doing work on a production database at a job. Then you can be very scared mweh

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✅ stateful versus stateless methods?