Ruminations About Enumerations

 

I have been busy refactoring my Windows Phone 7 game and I started using enumerations more to increase the readability of my code.  Some of the game rules are so complex and convoluted that I found enumerations a very handy way to express my intentions.  For example, consider this:

1 2 if (targetUnit.Equipment.EquipmentSubClass.EquipmentClass.EquipmentGroup.EquipmentGroupId == 0 3 && targetTile.Terrain.TerrainType.TerrainTypeId == 1 4 && targetUnit.CanMove 5 && targetUnit.CanAttack) 6 { 7 this.menuFactory.ShowUpgrade = true; 8 }

to this:

1 if (targetUnit.Equipment.EquipmentGroupEnum == EquipmentGroupEnum.Land 2 && targetTile.Terrain.TerrainTypeEnum == TerrainTypeEnum.Port 3 && targetUnit.CanMove 4 && targetUnit.CanAttack) 5 { 6 this.menuFactory.ShowUpgrade = true; 7 }

If you dropped into this project, which one would you understand quicker?  This readability comes with a cost though – I now have to create separate files of code that I need to maintain. A second problem is that I am duplicating data – the lookup values from my database are hard-coded into the business layer.  If I add a value to the database and want to use it in my business logic, I will have to recompile.  A final problem is one of naming – I have a class and an enum that means exactly the same thing but I don’t want to name them the same thing (see Domain specific language), even if used different namespaces.  In this example, I appended “enum” to the suffix of the class: TerrainType and TerrainTypeEnum.  Taking these problems in order:

Problem #1: separate code to maintain – Yes, though it seems like a small price to pay.  The trend in our industry is to have more classes/things that do only 1 thing (Single Responsibility Principle) so a large number of files is a natural side-effect.  Fortunately, VS2010 makes file cataloging easy so it does not really get in the way of developer productivity.

Problem #2: duplicate data.  Yes, but…. The enums are data that is to be used in design time (as part of the business/programming logic).  The data that is stored in the classes are for the end-user.  That data is volatile  and changes can be reflected at run-time without recompiling, mostly.  I would maintain that due to the separate audiences, it is ok to have 2 “things” represent the same data.  I would also argue that enums are only for classes that are lookups – reference tables in your database for example.  In that case, even if you make a change to a reference table and want to implement some additional logic in your code, guess what?  You are still recompiling.  You just have to remember to add that value to the enum – which should be fairly straightforward if your spent some time to make sure your projects are consistent and well-organized.

Problem #3 Naming.  Since the project now has two things (the class and the enum) representing the same data, what should be done about naming.  The .NET API/Framework Design Guidelines is not much help here – Color is an enum only, there is no color class.  If more colors are added/created, they are NOT reflected in the .NET Color enum, you have to use the RGB values.  I  appended the enum suffix on the name of the class because it is pretty clear the intention of the files:

image

I punted – but at least I punted consistently.

After all that, I find that my code is MUCH more readable and I am writing business rules much faster and finding my logic errors much quicker. 

As a side note, do you notice that some organizations they dub “SMEs” that are just walking enums?  For example, they can recite what ICD-9 code for a broken leg off of the top of their head.  I wonder if a well-designed system replaces this kind of expert….

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Using Lambdas To Increase Code Readability

I was having a spirited debate with Rob Seder yesterday about the use of lambdas – the question was weather using them increases or decreases the codes readability.  For example, here is a basic for…each:

1 foreach (Employee employee in employeeFactory.GetAllEmployees()) 2 { 3 if (employee.Name == "Moe") 4 { 5 Console.WriteLine(employee.ToString()); 6 } 7 }

Replacing with a lambda:

1 var moe = employeeFactory.GetAllEmployees().Where(e => e.Name == "Moe").FirstOrDefault(); 2 Console.WriteLine(moe.ToString());

Readability suffers for three reasons: the function chaining. the use of single letters for the variable, and the use of the var keyword.  A more readable use of lambda is like so:

1 List<Employee> employeeList = employeeFactory.GetAllEmployees().ToList(); 2 Employee selectedEmployee = employeeList.Where(employee => employee.Name == "Moe").FirstOrDefault(); 3 Console.WriteLine(selectedEmployee.ToString());

Taking the problems in reverse, Rob mentioned that he uses the var keyword when he is knocking something out, then he goes back and refactors the var keyword to the correct type.  I would agree with this.  As for the single varaible, I am less convinced that readability suffers because

  • Everyone does it – making this convention readability by default
  • You actually don’t use the variable – it is not returned or acted on beyond the line of code.

As for function chaining, I can see why readability suffers.  Breaking out the functions into logic units of work with each getting their own line seems reasonable.

Optimize Searching Using Value Types

As mentioned in my blog post here, I need to write a searching algorithm of hexes adjacent to the active unit to display movable/visible/attackable hexes.  The original code was a bit of a beast across 3 functions:

 

1 public List<Hex> GetTotalAdjacentHexes(Hex currentHex, Int32 maxDistance) 2 { 3 List<Hex> hexes = new List<Hex>(); 4 List<Hex> tempList = GetAdjacentHexes(currentHex); 5 foreach (Hex hex in tempList) 6 { 7 if (!InHexList(hexes,hex)) 8 GetAdjacentHexes(currentHex, hexes, hex, tempList, 0, maxDistance); 9 } 10 return hexes; 11 } 12 13 public void GetAdjacentHexes(Hex currentHex, List<Hex> hexes, Hex hex, List<Hex> currentList, int distanceCounter, int maxDistance) 14 { 15 distanceCounter++; 16 { 17 foreach (Hex tempHex in currentList) 18 { 19 hexes.Add(tempHex); 20 if (distanceCounter < maxDistance) 21 { 22 List<Hex> tempList = GetAdjacentHexes(tempHex); 23 GetAdjacentHexes(currentHex, hexes, hex, tempList, distanceCounter, maxDistance); 24 } 25 } 26 } 27 } 28 29 public List<Hex> GetAdjacentHexes(Hex currentHex) 30 { 31 32 List<Hex> adjacentHexes = new List<Hex>(); 33 Hex targetHex = null; 34 //Above 35 int targetColumnNumber = currentHex.ColumnNumber; 36 int targetRowNumber = currentHex.RowNumber - 1; 37 targetHex = GetHex(targetColumnNumber, targetRowNumber); 38 if (targetHex != null) 39 adjacentHexes.Add(targetHex); 40 //Top Left 41 targetColumnNumber = currentHex.ColumnNumber - 1; 42 if (currentHex.ColumnNumber % 2 == 0) 43 targetRowNumber = currentHex.RowNumber - 1; 44 else 45 targetRowNumber = currentHex.RowNumber; 46 targetHex = GetHex(targetColumnNumber, targetRowNumber); 47 if (targetHex != null) 48 adjacentHexes.Add(targetHex); 49 //Bottom Left 50 targetColumnNumber = currentHex.ColumnNumber - 1; 51 if (currentHex.ColumnNumber % 2 == 0) 52 targetRowNumber = currentHex.RowNumber; 53 else 54 targetRowNumber = currentHex.RowNumber + 1; 55 targetHex = GetHex(targetColumnNumber, targetRowNumber); 56 if (targetHex != null) 57 adjacentHexes.Add(targetHex); 58 //Below 59 targetColumnNumber = currentHex.ColumnNumber; 60 targetRowNumber = currentHex.RowNumber + 1; 61 targetHex = GetHex(targetColumnNumber, targetRowNumber); 62 if (targetHex != null) 63 adjacentHexes.Add(targetHex); 64 //Bottom Right 65 targetColumnNumber = currentHex.ColumnNumber + 1; 66 if (currentHex.ColumnNumber % 2 == 0) 67 targetRowNumber = currentHex.RowNumber; 68 else 69 targetRowNumber = currentHex.RowNumber + 1; 70 targetHex = GetHex(targetColumnNumber, targetRowNumber); 71 if (targetHex != null) 72 adjacentHexes.Add(targetHex); 73 //Top Right 74 targetColumnNumber = currentHex.ColumnNumber + 1; 75 if (currentHex.ColumnNumber % 2 == 0) 76 targetRowNumber = currentHex.RowNumber - 1; 77 else 78 targetRowNumber = currentHex.RowNumber; 79 targetHex = GetHex(targetColumnNumber, targetRowNumber); 80 if (targetHex != null) 81 adjacentHexes.Add(targetHex); 82 83 return adjacentHexes; 84 }

I recently had a duh moment when I tried to optimize the code for speed (replacing hexes with tiles) – each hex has an unique row/column value that I could use to calculate distance.  In addition, instead of looping and collecting heavy reference types, I am using 2 integers in 1 loop, so the performance is dramatically improved.  Finally, since I drop from 84 lines of code to 54, I am making my code more maintainable.

 

1 public List<Tile> GetTotalAdjacentTiles(Tile startTile, Int32 maxDistance) 2 { 3 List<Tile> tiles = new List<Tile>(); 4 int startingColumn = startTile.ColumnNumber - maxDistance; 5 if(startingColumn < 0) 6 { 7 startingColumn = 0; 8 } 9 int endingColumn = startTile.ColumnNumber + maxDistance; 10 if (endingColumn > Game.CurrentBoard.NumberOfColumns) 11 { 12 endingColumn = Game.CurrentBoard.NumberOfColumns; 13 } 14 15 int startingRow = startTile.RowNumber - maxDistance; 16 if (startingRow < 0) 17 { 18 startingRow = 0; 19 } 20 int endingRow = startTile.RowNumber + maxDistance; 21 if (endingRow > Game.CurrentBoard.NumberOfRows) 22 { 23 endingRow = Game.CurrentBoard.NumberOfRows; 24 } 25 26 Tile tile = null; 27 int combinedDistance = 0; 28 for (int i = startingColumn; i <= endingColumn; i++) 29 { 30 for (int j = startingRow; j <= endingRow; j++) 31 { 32 tile = GetTile(i, j); 33 if (!tiles.Contains(tile)) 34 { 35 combinedDistance = GetDistanceBetweenTwoTiles(startTile,tile); 36 if (combinedDistance <= maxDistance) 37 { 38 tiles.Add(tile); 39 } 40 } 41 } 42 } 43 44 //Remove Starting Tile 45 tiles.Remove(startTile); 46 47 return tiles; 48 } 49 50 public List<Tile> GetAdjacentTiles(Tile currentTile) 51 { 52 return GetTotalAdjacentTiles(currentTile, 1); 53 }