How to access a list outside a class.

Question

How to access a list outside a class.

FranK Duc 121

Hello,

I am trying to acces a list outside a class. I tried with public static but nothing. The list return different answers than if it called from OnRender class. Any suggestions!

 public class NEWSDBA : Indicator
    {

public static var listm = new List<double>();    //tried with private also

protected override void OnBarUpdate()
        {
foreach(var item in listm)
{
Value[0] = item;
}

        }


protected override void OnRender(ChartControl chartControl, ChartScale chartScale)
        {
            base.OnRender(chartControl, chartScale); 

//calculation to produce the list start here

       }


}

Thank you

3 answers

Your answer

Answer 1

Static class members are not part of the class instance by definition. Typically, a public property is used.

    public class MyClass
    {
        public List<double> myDouble { get; set; }

        public MyClass()
        {
            myDouble = new List<double>() { 1, 2, 3, 4, 5 };
        }
    }
    class Program
    {

        static void Main(string[] args)
        {
            MyClass myclass = new MyClass();
            foreach(double item in myclass.myDouble)
            {
                Console.WriteLine(item);
            }
        }
    }

Answer 2

FranK Duc 121

I get an error message saying :

NinjaScript File Error Code Line Column
NEWSDBA.cs 'NinjaTrader.NinjaScript.Indicators.Indicator.NEWSDBA (int, int)' is a 'method', which is not valid in the given context CS0119 78 34

I think you got it right but i dont know how to make it work, considering it is Ninjatrader software and not Visual studio. Any inputs?

 public class NEWSDBA : Indicator
    {
public List<double> listm { get; set; }



protected override void OnBarUpdate()
        {
NEWSDBA newsdba = new NEWSDBA();

 foreach(var item in NEWSDBA.listm)
             {
 Value[0] = item;
  }
        }


}

Thanks

AgaveJoe 30,126 Reputation points

2021-09-02T18:41:57.03+00:00

The code sample makes no logical sense. I'm not sure what you are trying to do.

Typically, any method that starts with "On" is a part of an event driven pattern. I'm guessing that List<double> is an event argument???
FranK Duc 121 Reputation points

2021-09-02T18:46:55.667+00:00

Cant say i am starting with c#

AgaveJoe 30,126

Cant say i am starting with c#

I do not understand your response. Maybe this is what you are trying to do??? The Program class updates the MyClass.myDouble property. The property is updated outside the class.

    public class MyClass
    {
        public List<double> myDouble { get; set; }

        public MyClass()
        {
            myDouble = new List<double>() { 1, 2, 3, 4, 5 };
        }
    }

    class Program
    {

        static void Main(string[] args)
        {
            MyClass myclass = new MyClass();
            foreach (double item in myclass.myDouble)
            {
                Console.WriteLine(item);
            }

            for(int i = 0; i < myclass.myDouble.Count(); i++)
            {
                myclass.myDouble[i] = i * 10;
            }

            Console.WriteLine("-----------");

            foreach (double item in myclass.myDouble)
            {
                Console.WriteLine(item);
            }
        }
    }

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FranK Duc 121 Reputation points

2021-09-02T19:01:15.607+00:00

No Joe i just want to access my listm in the OnRender class in the OnBarUpdate class.
Ninjatrader is a charting software they have two class to manipulate stock data. OnBarUpdate and OnRender.

II work in OR for practical reasons. I have a list of doubles in listm and i need to access those data in OBU to plot the numbers into the chart with the method :

AddPlot(Brushes.Yellow, "NEWSDBA");

To make it work listm must be extracted from OBU because AddPlot(Brushes.Yellow, "NEWSDBA"); cant work in OR.

So in OnRender i used the base.OnRender(chartControl, chartScale);

Now i cant reach my listm from OR if its not declare from outside OR, thats why i want to move my list outside the class, otherwise i cant access the numbers in the list from OBU.

Is it more clear?
FranK Duc 121 Reputation points

2021-09-02T19:15:00.48+00:00

Looks like a comment i made has been deleted.

I just want to have access to listm in OnBarUpdate because i need the data in the list to plot in the chart a line with the AddPlot(Brushes.Yellow, "NEWSDBA"); method.

If listm is not declared outside OnRender i cant access the data in OBU and i cant make the calculation in OBU to fill the list, it has to be in OR.

AddPlot wont workd in OR data need to be called from OBU.
AgaveJoe 30,126 Reputation points

2021-09-02T19:40:10.647+00:00

I just want to have access to listm in OnBarUpdate

And that is exactly what my last code sample illustrates.

My best guess is the 3rd party Ninjatrader charting API you are using is even driven and you are not following the Ninjatrader documentation. I recommend asking this question on the Ninjatrader support. I'm sure they can provide better assistance with their software.

Answer 3

P a u l 10,761

You're accessing listm like it's a static property. Did you mean to use newsdba here instead of NEWSDBA?:

foreach(var item in NEWSDBA.listm)

FranK Duc 121 Reputation points

2021-09-02T18:46:03.687+00:00

You are right, wrong spelling. But it does not solve the issue.
P a u l 10,761 Reputation points

2021-09-02T18:56:32.067+00:00

Do you need this line?

NEWSDBA newsdba = new NEWSDBA();

I'd assume you'd just want to foreach over the listm for the current instance, i.e.

foreach(var item in listm)

As long as listm is being initialised somewhere (like in the constructor as AgaveJoe posted) then that should work.

This line will also overwrite the first item in the Value array for every item in listm - is that deliberate?

Value[0] = item;
FranK Duc 121 Reputation points

2021-09-02T19:09:00.81+00:00

Without that line NEWSDBA newsdba = new NEWSDBA();
newsdba dont exist in that context.
FranK Duc 121 Reputation points

2021-09-02T19:17:29.967+00:00

Without that line newsdba dont exist.
P a u l 10,761 Reputation points

2021-09-02T19:23:13.467+00:00

But OnBarUpdate is an instance method, so you will already have an instance of NEWSDBA created somewhere that you're calling OnBarUpdate against.

At the moment that code creates a second instance inside of the OnBarUpdate of the first, then loops through the listm values for the second instance, rather than just using listm of the first instance.

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How to access a list outside a class.

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