Help Understanding c# Objects - Overclock.net

Dethredic · 10-10-09

So, I have some basic programming knowledge but I can't seem to understand objects, or a reason for using them until programs get really big.

I was asked to write a property to access (get) and mutate (set) the value of the circle's radius. Note that you will also need to recalculate the circumference of the circle when the radius is updated.

Code:

using System;

class Circle
{
    double radius;
    double circumference;

    public Circle( double r )
    {
        radius = r;
        circumference = 2.0d * Math.PI * radius;
    }
    
    // my additions start
    public double Radius
    {
    	get 
    	{ 
    		return radius; 
    	}
    	set 
    	{ 
    		radius  = value; 
    		circumference = 2.0d * Math.PI * radius;
    	}
    }
	// my additions stop
	
    public override string ToString( )
    {
        string s;

        s = string.Format( 
            "Radius = {0:F2} m, Circumference = {1:F2} m",
            radius, circumference );

        return s;
    }
    
}

I am not sure if that is correct, or how this would be used in a program, because there seems to be easier ways to do it.

I have read a bunch of google results but I can't say they helped.

Viscerous · 10-10-09

You shouldn't set the value of the circumference in that property. It's a radius property as you specified.

**BiG O** · 10-10-09

What you have is right. That's how you do getters and setters in C#. Not sure why you would think there's an easier way though.

You do, however, need to move the circumference statement out of the setter field. You could call it outside if you wanted.

Dethredic · 10-10-09

so would something like this be better:

Code:

    // my additions start
    public double Radius
    {
    	get 
    	{ 
    		return radius; 
    	}
    	set 
    	{ 
    		radius  = value; 
    	}
    }
    public double Circumference
    {
    	set
    	{
    		circumference = value;
    	}
    }
	// my additions stop

Spotswood · 10-10-09

Quote:

Originally Posted by Dethredic

Code:

    public double Circumference
    {
    	set
    	{
    		circumference = value;
    	}
    }

If it was me, I wouldn't store both the radius and the circumference, since when one is updated the other has to be updated as well:

Code:

    public double Circumference
    {
    	set
    	{
    		radius = RadiusFromCircumference(value);
    	}
    }
	
    private double RadiusFromCircumference(double circumference)
    {
        // TODO!
        return 0;
    }

dharmaBum · 10-11-09

Your first try was fine, but it would probably be best coding practise to define a function that resets the value of the circumference.

Quote:

reset_circ(){ circumference=2*pi*Radius; }

and replace your line setting the circumference with a call to this function (note you can do this in your constructor as well). This way, if in the future you need to update this code, let's say you need to put the area of a circle as another property, you only need to update this function.

This is the power of using objects. You are correct in saying there are probably much simpler ways of doing this specific assignment without using objects, but down the road it may so happen that this code needs to get modified for a larger purpose, and this is where OO programming starts to shine.

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Help Understanding c# Objects

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