Code Housekeeping - Part 3 - Eschew Boolean Method Parameters

This is Part 3 of the CodeHousekeeping Series.

Code Housekeeping refers to general rules of thumb that make code easier to read, digest, and modify for other developers, yourself included.

Today we will look at a simple concept - avoid boolean parameters.

My objection to this is nothing to do with functionality but everything to do with readability.

Take the following simplified example:

public class OrderProcessor
{
	public decimal ComputePrice(bool gross)
	{
		if (gross)
			return 100;
		return 84;
	}
}

On the surface this looks perfectly reasonable.

You pass true and you get back the GrossPrice. Pass false and get back the NetPrice.

The problem is when you see the code in the wild.

Quick, just by reading the code do you understand what the amount is going to represent?

You can argue that this isn’t an issue with a modern IDE - you can mouseover to see what the parameter represents.

Or you can decorate the parameter like this:

Slightly better but there are still problems:

1. What if I am not using an IDE - I could be reading the code on GitHub
2. Why do I need to mouseover things to understand the code
3. What, in fact, does passing true mean? That I get back the Gross or the Net

It is much clearer to use Enums for this purpose.

We create one like so:

public enum PriceMode
{
  Gross,
  Net
}

Then we create our type like this:

public class OrderProcessor
{
  public decimal ComputePrice(PriceMode mode)
  {
    switch (mode)
    {
      case PriceMode.Net:
      	return 84;
      default:
      	return 100;
    }
  }
}

We invoke it like this:

var proc2 = new OrderProcessor.v2.OrderProcessor();
// Compute and return the price
amount = proc2.ComputePrice(PriceMode.Gross);

Console.WriteLine(amount);

This has the following benefits:

1. Easier to read
2. Easier to to parse & undertand
3. Easier to extend - with boolean you have only two options

TLDR

Generally, use enum over boolean as parameters.

The code is in my GitHub.

Happy hacking!