Best OO practice - passing in caller reference to interface methods

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I have a situation where I find myself needing to call methods that reside in the caller class. Should i pass 'this' as a parameter, as I've done below, or should I be raising events back up to the caller? Or is there another way that this is normally done?

What I have tried:

The example below works, but feels a bit dirty. I feel like there should be a better way.

C#

void Main()
{
	var stack = new Stack();
	stack.Push(1);
	stack.Push(2);
	stack.Push(3);
	stack.Push(4);
	
	var specialStack = new SpecialStack(stack, new TriplePopper());
	specialStack.SpecialPop();
	// stack now only has a count of 1
}

public class SpecialStack
{
	IPopper _popper;
	Stack _stack;

	public SpecialStack(Stack stack, IPopper popper)
	{
		_stack = stack;
		_popper = popper;
	}

	public void SpecialPop()
	{
		_popper.SpecialPop(this);
	}

	public void PopOnce()
	{
		_stack.Pop();
	}

}

public interface IPopper
{
	void SpecialPop(SpecialStack stack);
}

public class DoublePopper : IPopper
{
	public void SpecialPop(SpecialStack stack)
	{
		stack.PopOnce();
		stack.PopOnce();
	}
}

public class TriplePopper : IPopper
{
	public void SpecialPop(SpecialStack stack)
	{
		stack.PopOnce();
		stack.PopOnce();
		stack.PopOnce();
	}
}

Posted 17-Aug-20 20:36pm

TheRedEye

Updated 17-Aug-20 22:10pm

v3

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2 solutions

Solution 2

I think what you want to do here can be done so much more simply by extending the 'Stack Class:

C#

using System.Collections.Generic;
using System.IO;

namespace WFTemplate_Aug2020
{
    public class StackPopEx<T> : Stack<T>
    {
        public StackPopEx(params T[] values)
        {
            foreach(T itm in values) Push(itm);
        }

        public void PopEx(int npops)
        {
            if (npops <= 0)
            {
                throw new InvalidDataException($"npops = {npops}  <= 0");
            }

            if (npops > Count)
            {
                throw new InvalidDataException($"npops = {npops} greater than stack count: {Count}");
            }

            for (int i = 0; i < npops; i++)
            {
                Pop();
            }
        }
    }
}

Posted 17-Aug-20 22:10pm

BillWoodruff

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OriginalGriff · Accepted Answer · 2020-08-17T20:47:00

Raise events back up to the caller: a class should never know who or what called it, so it shouldn't access methods in them. If you do, you lock the design together so that both you can't change one without considering the effects on the other, and you can't reuse the classes independently.