CODEWITHSUNDEEP
c#classoopmethods
Guy Lee
Guy Lee

Reputation: 193

C# How to access method of a class from another class it instantiates?

I have 2 classes where 1 class is like the main class and I have a secondary class which is instantiated from the main class. How am I able to use the main class' method from the secondary class. Here's code to give an illustration of what I want. 

public class MainClass
{
    private SecondaryClass secondaryClass;
    private int testValue;

    public MainClass()
    {
        this.secondaryClass = new SecondaryClass();
        testValue = 0;
    }

    public void updateTestValue (int val)
    {
        testValue = val;
    }
}

public Class SecondaryClass : Form
{
    public SecondaryClass() 
    {

    }

    private void button1_click(Object sender, EventArgs e)
    {
        // I want to be able to do this:
        primaryClass.updateTestValue(100);
    }

}

Upvotes: 0

Views: 276

Answers (3)

Zoran Horvat
Zoran Horvat

Reputation: 11301

You can make classes communicate without having one derive from another.

public class MainClass
{
    private SecondaryClass secondaryClass;
    private int testValue;

    public MainClass()
    {
        this.secondaryClass = new SecondaryClass(this.UpdateTestValue);
        testValue = 0;
    }

    public void UpdateTestValue (int val)
    {
        testValue = val;
    }
}

public class SecondaryClass : Form
{
    private Action<int> UpdateValue { get; }

    public SecondaryClass(Action<int> updateValue) 
    {
        this.UpdateValue = updateValue;
    }

    private void button1_click(Object sender, EventArgs e)
    {
        this.UpdateTestValue(100);
    }
}

In this organization, primary class is passing a delegate to its own instance-level method when it creates the secondary class. Secondary class calls that delegate when appropriate, without ever knowing what function that is.

This is the example of the callback pattern.

There are other variants of the same idea. For example, primary class could implement an interface which defines the UpdateValue method. Then, it passes this reference to every object which needs access to that method. Other objects, like an object of secondary class, would then simply call a method of that interface, once again not knowing that it is in fact the primary class they are referencing.

public interface IListener
{
    void Update(int value);
}

public class MainClass : IListener
{
    private SecondaryClass secondaryClass;
    private int testValue;

    public MainClass()
    {
        this.secondaryClass = new SecondaryClass(this);
        testValue = 0;
    }

    public void Update(int val)
    {
        testValue = val;
    }
}

public class SecondaryClass : Form
{
    private IListener Listener { get; }

    public SecondaryClass(IListener listener) 
    {
        this.Listener = listener;
    }

    private void button1_click(Object sender, EventArgs e)
    {
        this.Listener.Update(100);
    }
}

The price of this solution is one additional type in the system (interface IListener), and the benefit is that you can avoid working with delegate syntax. Delegates have a drawback that their arguments have no names, and therefore you can easily make a bug if you mix them up.

Upvotes: 3

JARRRRG
JARRRRG

Reputation: 926

A class can only have one base class

What you could do is move the :Form base class up to the primary class and then from your secondary class have it's base class as Primary class and use the functions as follows.

public class PrimaryClass : Form
{
    private int testValue;

    public void PrimaryClassMethod()
    {
        Console.WriteLine("Method from Primary Class");
    }

    public void UpdateTestValue (int val)
    {
        testValue = val;
    }
}

public class SecondaryClass : PrimaryClass
{
    public void CallPrimaryClassMethod()
    {
        this.PrimaryClassMethod();
        this.UpdateTestValue(10000);
    }

}

https://dotnetfiddle.net/PC2WVu

Upvotes: 0

Robert McKee
Robert McKee

Reputation: 21487

public class MainClass: Form
{
    private int testValue;

    public MainClass()
    {
        testValue = 0;
    }

    public void updateTestValue (int val)
    {
        testValue = val;
    }
}

public class SecondaryClass : MainClass
{
    public SecondaryClass() 
    {

    }

    private void button1_click(Object sender, EventArgs e)
    {
        // I want to be able to do this:
        updateTestValue(100);
    }
}

Upvotes: 0

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