Easy To Read != Easy To Understand

I ran into this code a while back:

   1: public abstract class ScanPrefixSpecification : IScanSpecification

   2: {

   3:     public abstract IEnumerable<string> BarcodePrefixesFilter { get; }


   5:     public bool IsSatisfiedBy(string item)

   6:     {

   7:         return BarcodePrefixesFilter.Where(item.StartsWith).Any();

   8:     }


  10:     public string GetScanFrom(string scanString)

  11:     {

  12:         foreach (var prefixFilter in BarcodePrefixesFilter.Where(scanString.StartsWith))

  13:         {

  14:             return scanString.Substring(prefixFilter.Length);

  15:         }

  16:         return "";

  17:     }

  18: }

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There isn’t anything wrong with this code from a technical standpoint. It does exactly what it needs to do and it provides a specific point of functionality in our system. By reading the code and by reading the tests around this code, I can see what this class does:

  • it’s a basic specification pattern where the scanned item satisfies the specification when the “item” starts with any of the strings found in the BarcodePrefixesFilter list
  • and it removes the first match found in the BarcodePrefixesFilter list from the beginning of the “scanString”; or returns an empty string if no matches were found

Ok, that’s great… now, why does it do that? Where does this code express the needs of the business; the understanding of why those characters need to be removed from the front of the scanned string? How much additional code am I going to have to read to understand the context of this code? How long will it take me to understand what functionality this code facilitates, from a functional view of the system?

… easy to read is not the same as easy to understand. Be sure your code is understandable, not just readable; and the only way to do that is for someone else to look at your code and work with it.

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