C#•3y ago

can someone help me with my abstract class

I've created my abstract classes and no we can't make instances of them, but i keep getting errors even after following youtube videos to the t.

here's my first file using abstract classes

namespace Module_9
{
    public abstract class RailroadCar
    {
        //data fields
        protected double length;

        //constr
        protected RailroadCar(double length = 0.00)
        {
            SetLength(length);
        }

        //GETTERS
        /** Returns length of solid.
            @return: solid length
        */
        public double GetLength(double length) { return length; }

        /** Updates length of solid.
            @return: updated length.
        */
        //SETTERS
        public void SetLength(double length) { this.length = length;}

        /** Calculates the volume of the solid.
            @return: calculated volume of the solid
        */
        public abstract double Volume();
    }
}

namespace Module_9
{
    public abstract class RailroadCar
    {
        //data fields
        protected double length;

        //constr
        protected RailroadCar(double length = 0.00)
        {
            SetLength(length);
        }

        //GETTERS
        /** Returns length of solid.
            @return: solid length
        */
        public double GetLength(double length) { return length; }

        /** Updates length of solid.
            @return: updated length.
        */
        //SETTERS
        public void SetLength(double length) { this.length = length;}

        /** Calculates the volume of the solid.
            @return: calculated volume of the solid
        */
        public abstract double Volume();
    }
}

namespace Module_9
{
    public abstract class RailroadCar
    {
        //data fields
        protected double length;

        //constr
        protected RailroadCar(double length = 0.00)
        {
            SetLength(length);
        }

        //GETTERS
        /** Returns length of solid.
            @return: solid length
        */
        public double GetLength(double length) { return length; }

        /** Updates length of solid.
            @return: updated length.
        */
        //SETTERS
        public void SetLength(double length) { this.length = length;}

        /** Calculates the volume of the solid.
            @return: calculated volume of the solid
        */
        public abstract double Volume();
    }
}

namespace Module_9
{
    public abstract class RailroadCar
    {
        //data fields
        protected double length;

        //constr
        protected RailroadCar(double length = 0.00)
        {
            SetLength(length);
        }

        //GETTERS
        /** Returns length of solid.
            @return: solid length
        */
        public double GetLength(double length) { return length; }

        /** Updates length of solid.
            @return: updated length.
        */
        //SETTERS
        public void SetLength(double length) { this.length = length;}

        /** Calculates the volume of the solid.
            @return: calculated volume of the solid
        */
        public abstract double Volume();
    }
}

DinnyOP•11/10/23, 10:33 PM

in my main program, i know we can't do, for example, " RailroadCar railroadcar = new RailroadCar()," but in the exmple on youtube, i could do something like "RailroadCar railroadcar = new TankCar();" but that doesn't work either. I am still new and trying to understand, but I am so stuck

Angius•11/10/23, 10:34 PM

Does TankCarTankCar inherit from RailroadCarRailroadCar?

DinnyOP•11/10/23, 10:34 PM

yes it does

DinnyOP•11/10/23, 10:35 PM

one moment

Angius•11/10/23, 10:35 PM

It has to work, then

MODiX•11/10/23, 10:35 PM

Angius

REPL Result: Success

abstract class Foo {}
class Bar : Foo {}

Foo f = new Bar();

abstract class Foo {}
class Bar : Foo {}

Foo f = new Bar();

Compile: 566.461ms | Execution: 36.685ms | React with ❌ to remove this embed.

DinnyOP•11/10/23, 10:35 PM

namespace Module_9
{
    public abstract class TankCar : RailroadCar
    {
        //data fields
        private double radius;

        protected TankCar(double radius, double length) : base(length)
        {
            SetRadius(radius);
            SetLength(length);

        }

namespace Module_9
{
    public abstract class TankCar : RailroadCar
    {
        //data fields
        private double radius;

        protected TankCar(double radius, double length) : base(length)
        {
            SetRadius(radius);
            SetLength(length);

        }

DinnyOP•11/10/23, 10:35 PM

here's a tiny bit og tankcar

DinnyOP•11/10/23, 10:35 PM

AAngius It has to work, then

DinnyOP•11/10/23, 10:35 PM

i don't see what I am doing wrong then

Angius•11/10/23, 10:35 PM

Your constructor is protected, that might be why you're getting errors

DinnyOP•11/10/23, 10:36 PM

bc i keep getting the same error :///

Angius•11/10/23, 10:36 PM

But it's hard to tell without seeing the actual error

DinnyOP•11/10/23, 10:36 PM

ill take a picture of it one momebt plz

DinnyOP•11/10/23, 10:37 PM

DinnyOP•11/10/23, 10:39 PM

should they all be public instead of protected ?

Angius•11/10/23, 10:40 PM

Well

Angius•11/10/23, 10:40 PM

Your TankCarTankCar itself is abstractabstract

Angius•11/10/23, 10:40 PM

And, as you said, can't instantiate abstract classes

DinnyOP•11/10/23, 10:42 PM

one moment lemme try fixing that

DinnyOP•11/10/23, 10:46 PM

okay i made them now a public class derived from the abstract classes but it’s still not working

Angius•11/10/23, 10:47 PM

Is the derived class still abstract?

DinnyOP•11/10/23, 10:53 PM

yes

DinnyOP•11/10/23, 10:53 PM

that's how my prof is doing it too

Angius•11/10/23, 10:56 PM

It's not

Angius•11/10/23, 10:56 PM

It cannot be

Angius•11/10/23, 10:56 PM

Because instantiating an abstract class is not possible

Angius•11/10/23, 10:56 PM

The base class can be abstract

Angius•11/10/23, 10:56 PM

But classes that inherit from it can be not-abstract

DinnyOP•11/10/23, 10:57 PM

oh no wait sorry

DinnyOP•11/10/23, 10:57 PM

the base class is abstract

DinnyOP•11/10/23, 10:57 PM

the derived classes are not

DinnyOP•11/10/23, 10:57 PM

they're all public

Angius•11/10/23, 10:57 PM

And in your example the derived class is still abstract

Angius•11/10/23, 10:57 PM

Hence the error

DinnyOP•11/10/23, 10:58 PM

oh wait let me show up my updated version

DinnyOP•11/10/23, 10:58 PM

namespace Module_9
{
    public abstract class RailroadCar
    {
        //data fields
        private double length;

        //constr
        protected RailroadCar(double length = 0.00)
        {
            SetLength(length);
        }

        //GETTERS
        /** Returns length of solid.
            @return: solid length
        */
        public double GetLength() { return length; }

        /** Updates length of solid.
            @return: updated length.
        */
        //SETTERS
        public void SetLength(double length) { this.length = length;}

        /** Calculates the volume of the solid.
            @return: calculated volume of the solid
        */
        public abstract double Volume();
    }
}

namespace Module_9
{
    public abstract class RailroadCar
    {
        //data fields
        private double length;

        //constr
        protected RailroadCar(double length = 0.00)
        {
            SetLength(length);
        }

        //GETTERS
        /** Returns length of solid.
            @return: solid length
        */
        public double GetLength() { return length; }

        /** Updates length of solid.
            @return: updated length.
        */
        //SETTERS
        public void SetLength(double length) { this.length = length;}

        /** Calculates the volume of the solid.
            @return: calculated volume of the solid
        */
        public abstract double Volume();
    }
}

DinnyOP•11/10/23, 10:58 PM

here's the base abstract class

DinnyOP•11/10/23, 10:59 PM

namespace Module_9
{
    public class TankCar : RailroadCar
    {
        //data fields
        private double radius;

        public TankCar(double radius = 0.0, double length = 0.0) : base(length)
        {
            SetRadius(radius);
            SetLength(length);

        }

        //GETTERS
        /** Returns radius of solid.
            @return: solid radius.
        */
        public double GetRadius() { return radius; }



        //SETTERS
        /** Updates radius of solid.
            @return: updated radius
        */
        public void SetRadius(double radius) { this.radius = radius; }

        /** Calculates the volume of the solid.
            @return: calculated volume of the solid
        */
        public override double Volume() { return Math.PI * Math.Pow(radius, 2) * GetLength(); } 
    }
}

namespace Module_9
{
    public class TankCar : RailroadCar
    {
        //data fields
        private double radius;

        public TankCar(double radius = 0.0, double length = 0.0) : base(length)
        {
            SetRadius(radius);
            SetLength(length);

        }

        //GETTERS
        /** Returns radius of solid.
            @return: solid radius.
        */
        public double GetRadius() { return radius; }



        //SETTERS
        /** Updates radius of solid.
            @return: updated radius
        */
        public void SetRadius(double radius) { this.radius = radius; }

        /** Calculates the volume of the solid.
            @return: calculated volume of the solid
        */
        public override double Volume() { return Math.PI * Math.Pow(radius, 2) * GetLength(); } 
    }
}

DinnyOP•11/10/23, 10:59 PM

heres the TankCar class

Angius•11/10/23, 10:59 PM

Now it should work

DinnyOP•11/10/23, 10:59 PM

why is there still a squiggle ugh

DinnyOP•11/10/23, 10:59 PM

lemme refrsh plz hold

Angius•11/10/23, 11:00 PM

What does the squiggle say?

DinnyOP•11/10/23, 11:00 PM

okay i just needed to save and refresh

DinnyOP•11/10/23, 11:00 PM

VS does that soemetines, it's annoying

DinnyOP•11/10/23, 11:00 PM

tysm !!

DinnyOP•11/10/23, 11:00 PM

u were a big help

Angius•11/10/23, 11:01 PM

Anytime

can someone help me with my abstract class

Similar Threads

Similar Threads

Similar Threads