Comments on: Expressive Code: Good Variable Names Instead Of Magic Values And Calculations

By: Ufuk Kayserilioglu

Ufuk Kayserilioglu — Sun, 25 Apr 2010 10:45:23 +0000

I am all for the more readable code; however, the two versions of the code do not produce the same output. In the first one, for the second DrawLine call you have a “ClientRectangle.Width”. In the more readable version that gets changed to “right”, which actually stands for “ClientRectangle.Width – 1″.

Am I missing something?

By: Andrew Hare

Andrew Hare — Fri, 23 Apr 2010 12:33:55 +0000

This is really good advice as magic values really hurt the readability and maintainability of your code. I would argue that this is a hallmark of a declarative style of coding (being more expressive and ultimately more readable). I wrote a similar article myself (http://togaroga.com/2010/03/writing-better-code-its-imperative-that-you-are-declarative/) that focused more on method names than variable names but the concept is the same – declarative code is better for everyone!

By: derick.bailey

derick.bailey — Thu, 22 Apr 2010 18:53:13 +0000

@dave-ilsw

if i was drawing a line along the bottom of the button, then yes it would matter and it should have a -1 on the bottom variable. but in this case, i am only drawing on the left, top, and right borders so it doesn’t matter.

By: John Sonmez

John Sonmez — Thu, 22 Apr 2010 18:18:56 +0000

@David

I like that one.

By: David Pendray

David Pendray — Thu, 22 Apr 2010 17:39:22 +0000

Is 8 extra setup lines excessive? If not, I’d put forward:

int left = 0;
int right = ClientRectangle.Width – 1;
int top = 0;
int bottom = ClientRectangle.Height;

var leftTop = new Point(left, top);
var rightTop = new Point(right, top);
var leftBottom = new Point(left, bottom);
var rightBottom = new Point(right, bottom);

graphics.DrawLines(outlinePen, new[] { leftBottom,
leftTop,
rightTop,
rightBottom });

With the final call reading: “leftBottom to leftTop to RightTop to RightBottom”.

By: PatrickM

PatrickM — Thu, 22 Apr 2010 17:07:18 +0000

That’s one of the goals for the new syntax in C# 4.0:

If you have a method:
public void Do(string action, int time);

You can optionally call it this way:
Do(action: “Execute”, time: 5);

And by the way, the parameter ordering does not have to be the same as the definition:
Do(time: 5, action: “Execute”);

Regards,

By: dave-ilsw

dave-ilsw — Thu, 22 Apr 2010 16:03:47 +0000

Should bottom subtract one from Height like right subtracts one from Width?

By: John Sonmez

John Sonmez — Thu, 22 Apr 2010 14:38:06 +0000

Whoops that was wierd, let me try one more time.

private class LineSegment
{
public int StartX { get; set; }
public int EndX { get; set; }
public int StartY { get; set; }
public int EndY { get; set; }
}

int left = 0;
int right = ClientRectangle.Width – 1;
int top = 0;
int bottom = ClientRectangle.Height;

IList lineSegments = new List {{StartX = left, StartY = top, EndY = left, EndY = bottom},
{StartX = left, StartY = top, EndY = right, EndY = top},
{StartX = right, StartY = top, EndY = right, EndY = bottom}};

foreach(var lineSegment in lineSegments)
{
graphics.DrawLine(outlinePen, lineSegment.StartX, lineSegment.StartY, lineSegment.EndX, lineSegment.EndY);
}

By: John Sonmez

John Sonmez — Thu, 22 Apr 2010 14:32:01 +0000

Good example. I have written the same code before and been confused, because I didn’t do what you are suggesting here.

Here is an even clearer version at the cost of some more code:

private class LineSegment
{
public int StartX { get; set; }
public int EndX { get; set; }
public int StartY { get; set; }
public int EndY { get; set; }
}

StartY, lineSegment.EndX, lineSegment.EndY);
}