XNA Game – Rotation – Discovering whether words have been made – Part 12


In this post I am going to go through the code that I have designed and written to detect if the player has made a word.  As stated in previous blog posts the player can make a word either vertically or horizontally.  The word has to have a minimum length.

The first thing that I needed to do was add a new property to the Square class CanUseInWord.  This is a bool that says whether that square can be used as a part of a word.  The reason for adding this is that I am currently thinking that I am going to have squares falling down from outside of the board, this will allow the player to see which squares will enter the board when they make a word.  I need a way to tell if the square can be used as a part of a word.  This will also allow me to put the game into a different mode that I have an idea about (more on that in later posts).  All of the squares that are selectable ie all of the ones that get filled with letters are eligible to be used in a word so currently I have set that property using the same logic.  I have obviously added a unit test for that in the board creation specs.

Next I need to design a collection to hold all of the possible words that the user can play.  This collection is hidden behind the interface IWordList which has one property Words which returns an IEnumerable<string>.  I have designed a factory to populate the word list, the default factory implementation populates the word list from a file.

Now that I can create a word list so I know all of the possible words a player can play, I need a way to check those words against every possible word in the board.  To do this I have designed an interface IWordChecker that has one method Check.  Check returns an IEnumerable<IWord> which is all of the words which have been found (if any) and it takes an IEnumerable<IEnumerable<Square>> (ie either all of the board’s columns or rows).  IWord is a simple interface that allows me to represent a collection of squares as a word.  It has two properties one which contains the string value that the list of squares represent and another which is the total value of those letters in points.

All of the above code is unit tested but I have left out the unit tests as they are straight forward.  If you wish to see them you can grab the code from github and check them out.  The interesting unit tests are the ones around checking for the existence of words in the board ie testing WordChecker.  I have designed 6 unit tests to do this:

1.  Check that if you have a set of squares that make a known word but all of the squares are squares in which the squares cant be used in a word then make sure that no words are returned.

2.  Check that a word is returned when a known word is in the list of squares that are passed in

3.  Check that two words are returned when two words are in the list of squares that are passed in (simulating two words being made in one row or column)

4.  Check that two words are returned when two words are in the list of squares and the words share letters e.g. HOUSEED should return HOUSE and SEED both words sharing the S and E

5.  Check that two words are returned when two words are in different lists in the lists of squares that are passed in (simulating that two words are made in two different rows or columns)

6.  Check that if there are no matching words in the lists that are passed in then no words are returned

To implement the code to check every possible word in the grid we first need to extract every possible word of a certain length.  We can do this with the following code

private IEnumerable<IWord> GetWordsOfLength(IEnumerable<Square> squares, int length)

    for (int i = 0; i + length <= squares.Count();  i++)

        var currentWordSquares = squares.Skip(i).Take(length);

        if (currentWordSquares.All(s => s.CanUseInWord))
            yield return new Word(currentWordSquares);

This private method works first by looping through all of the numbers from 0 to the total number of squares minus length of the words you are searching for.  Inside the loop the first thing we do is we skip to the starting square for the loop.  e.g. for the first iteration we will start at square 0.  The take statement then takes as many squares as we want this of course is the length of the word.  Next we check to make sure that all of those squares can be used in the word.  If all of those squares can be used in the word then we return that as a word from the grid.

public IEnumerable<IWord> Check(IEnumerable<IEnumerable<Square>> squares)
    var foundWords = new List<IWord>();

    foreach (var squareList in squares)
        for (int j = GameConstants.MIN_WORD_LENGTH; j <= squareList.Count(); j++)

            var words = GetWordsOfLength(squareList, j);

            foundWords.AddRange(words.Where(w => _wordList.Words.Contains(w.ToString())));



    return foundWords;

The method above completes the code for checking every word and passes all of the unit tests.  This code is pretty simple.  All we are doing is iterating around each list of squares ie basically looping around all of the rows or columns.  For each list of squares we loop around getting every word in that list of every length starting at the minimum word length and ending at the number of squares in the list (as obviously its impossible to have a word longer than that).  Once we have returned every possible word contained in that list all we have to do now is simply check to see if any of those words are in our word list and if so add them to the results.

That is all the code we need to implement word checking.  It’s good when a complex problem like this gets solved with a few simple lines of code.  It shows that we have broken our classes down and given them single responsibilities.  Because we have designed our unit tests upfront we have got confidence that our code works.  That is the beauty of TDD.

As always you can download the latest version of the code on Github.  Switch to the part12 branch to see the code at this point.  As always comments welcome.  Instructions on how to download the code from github or get in contact can be found on this page.



XNA Game – Rotation – Adding AutoFac IoC Container – Part 11


Now that I have the game starting to take shape (well that animations working and drawing the board) I have decided to put in an IoC container to get rid a lot of the custom wire up code, aka the following code block:

_board = new BoardFactory().Create();
var boardFiller = new BoardFiller(new StandardTileFactory(new LetterLookup()));

Func getMainSelectedSquare = () =&gt; _board.GetMainSelectedSquare();

var textureLoader = new TextureLoader(s =&gt; Content.Load(s));
		    _itemDrawerFactory =
		        new ItemDrawerFactory(new List
		                                      new SquareDrawer(
		                                          new TileTextureFactory(new List
		                                                                         new BlankTileTextureCreator(textureLoader),
		                                                                         new StandardTileTextureCreator(textureLoader)
		                                          new SquareColourSelector(),
		                                          new SquarePositionCalculator(getMainSelectedSquare),
		                                          new SquareOriginCalculator(getMainSelectedSquare))

		    var itemAnimatorFactory = new ItemAnimatorFactory(new List {new RotationAnimator()});

            _animationEngine = new AnimationEngine(itemAnimatorFactory, _itemDrawerFactory, _board.GetAnimatables);

            _currentPos = new Point(4, 4);
            _squareSelector = new SquareSelector();
            _squareSelector.Select(_board, _currentPos.X, _currentPos.Y);

            _selectionRotatator = new SelectionRotatator();

I think you will agree that the above code is a bit long winded because of course we are providing all of the dependencies manually to every constructor.

The first thing that I want to do is write a module to install classes by convention.  By registering by convention I mean if I have an interface called ITest and it’s implemented by a class called Test then that class will get installed automatically as it’s name is the same as the interface without the leading ‘I’.

Registering classes by convention is a good thing to do as one of the main reasons we use dependency injection (other than to reduce coupling) is to allow easy unit testing of our components.  However, when we come to use these components in the application it can get a bit long winded to register all of them one by one.   I know most IoC containers support auto registration of all classes by scanning your assemblies but this is not what I want either.  The reason is that if I implement an interface with a class that I intend to always use as the implementation of that interface then I will give it a name so that it’s installed by convention.  If I intend to swap the component out then I will use a different class name so that I have to implicitly install it.  I know you can never really say that you will always use a certain concrete implementation of an interface but what I am saying is that for the foreseeable future that is the implementation I will be using.

The IoC container that I have chosen to use is AutoFac.  Mainly because I have quite a bit of experience with using Castle and AutoFac and I prefer the syntax of AutoFac over Castle.  For what I want to do with IoC any of the main IoC containers would do the job.

Ok so on with writing my module (that is the name of installers in AutoFac) to install classes by convention I need a unit test.  This is quite a simple test:

var container = default(IContainer);
var result = default (ITest);

"Given I have installed the instant convention installer with this assembly".Context(() =>
                    var containerBuilder = new ContainerBuilder();
                        .RegisterModule(new InterfaceConventionModule(new[] { typeof(ITest).Assembly }));
                     container = containerBuilder.Build();

"When I resolve an ITest interface".Do(() => result = container.Resolve());

"Then the returned type should be a Test class".Observation(() => result.ShouldBeOfType());

The reason that my installer takes an array of assemblies is that it provides me with a neat way of choosing which assemblies to consider when installing by convention.  So when I am unit testing (as I am above) all I need to do is pass in the current assembly.  Obviously in the main code I will pass in all of the assemblies that I am using in the game. Implementing this installer is a pretty simple method:

protected override void Load(ContainerBuilder builder)
        .Where(t =&gt; t.GetInterfaces().Any(i =&gt; i.Name.TrimFirstChar('I').Equals(t.Name)))

TrimFirstChar is a simple extension method that I have written on string that simply chops off the first character if the character passed in matches, if it doesn’t then it returns the string that’s passed in.

The only other thing to do is write a few installers to install the classes that haven’t been installed by convention.  The installers are pretty mundane so I won’t list them here, if you want to see them pull down the latest version of the code and view branch part11.

Now that we can install all of the classes that we need all we need to do is fire up the container in the program start method, resolve the RotationGame class and call run on it:

using(var container = new Builder().Build())
    var childContainerBuilder = new ContainerBuilder();

    using (var game = container.Resolve())

Pretty straight forward. Now in our game we can specify all of the dependencies in the constructor and AutoFac will do the rest.  Nearly all of the first block of code can be removed 🙂

In the future I want to use the IoC container to swap out some of the components to make the game more difficult as the player progresses. This means that all of my code should stay the same and to progress levels all I should have to do is register different classes with the container. That’s the plan anyway for a later post.

As always if you want to get the latest version of the code you can do so from github, I have marked the code at this point as part11.

XNA Game – Rotation – Implementing the rotation animations – Part 10


Now that I have the graphics plumbed in the next step is to start to implement the rotation animation (after all that is what the game is named).

Before I go into how I have implemented the animations, a quick word about what has changed in the solution.  I have tidied up some of the code.  Firstly I have put the code that gets the textures for the drawable items behind a factory, this allows that code to be abstracted away.  Next I have introduced a constants class.  This class is responsible for setting different things like the colours of the tiles, by having a constants class I have one place in which I can tweak the game.  Obviously being a constants class all of these variables get compiled into the code.

Last post I naively stated that I was doing a lot of redundant drawing by redrawing every single item for every single frame.  I have since read that this is the way that the XNA framework works.  Normally it is more efficient to just redraw everything in a frame rather than calculate what has moved and just redraw that.  This makes sense, but means that I’ve had to go a slightly different path as to how I am going to do the animations.

When the player presses a button to rotate the squares this key press gets picked up in the update method.  Then the rotate right or left method is called on the square rotator and the squares are updated instantly in the board in memory.  This means that the next time the draw method gets called (i.e. a maximum of 1/60 of a second away) the board will instantly get redrawn with the tiles in the new position.  This is not what we want.  We want the tiles to animate round and finish in their final resting place in a smooth animation.

The way that the XNA framework implements rotations is in one of the overloads to the spritebatch’s draw method.  The overload takes a vector to represent the sprites position in space, a vector for the origin of rotation and a float for the amount of rotation in radians.

With the above knowledge of how the XNA framework handles rotations the trick to get our animations to work is to change the way that we draw our sprites for the tiles on the board.  The first implementation that we saw in part 9 just looped round all of the tiles and drew them at a specific point in space i.e. the first tile was drawn at 0, 0 the next at 40, 0 (40 being the width of a tile) and so on.  What we need to do is change this and use the overload of the draw method.  Except that we need to specify a position of the centre of the currently selected square, an origin of the offset from the currently selected square back to the point in space where we want to draw the square and a rotation of 0 degrees (for now).

For example when the centre square is selected (as is the default starting position) we set the position of the top left square to 180, 180 which is the exact centre of the selected square (tile).  A square is 40×40 so its 4.5 squares to the centre in both directions (4.5×40 = 180).  Next we need to get the offset from this point back to the top left corner of where we want to draw the square and pass that in as the origin.  In this case it’s -180, -180.  Obviously the degrees of rotation is 0.

To calculate these values I have introduced two new classes SquarePositionCalculator and SquareOriginCalculator.  These classes both have one method and are responsible for calculating a square’s position and a square’s origin respectively according to the currently selected square.  To see the full unit tests and implementation of both of these classes see the source code.  Now we have these classes all we need to do is inject them into the SquareDrawer class and call them to get the vectors out for when we draw the square.

Now that we have overcome that obstacle all that is left to do to animate the selection is to wrap the draw method with something that works out which squares are selected and slowly changes the angle of rotation.

To do this I have setup some new interfaces.  Firstly I have change the IDrawableItem to IAnimatableItem as for now everything that is animatable is drawable so IDrawableItem became redundant.  One might argue that I could need IDrawableItem again in the future.  That is true and if I need it again then I will add it back in.  But I don’t like leaving dead code hanging round in case I might need it in the future.  Doing this leads to code smell and can mean when people look at the code in the future they have a hard time following it when there are unused methods and classes all over the place.

The next interface that I need to define is a type of animation.  For now there is only one type of animation a rotation animation, the interface I have defined is IRotationAnimationItem that has two properties a direction (clockwise/anti-clockwise) and an angle of rotation (I’m going to work in degrees as I find that easier than radians and I can simply convert this before I call draw).  IRotationAnimationItem also implements the IAnimatableItem interface (obviously as if an item supports the rotation animation then it is obviously animatable).

To get the animation for the current item I have again used the factory pattern.  I have defined an interface IItemAnimator that has two methods CanAnimate and Animate.  This pattern is almost identical to how the item drawers worked.  I have a factory class that takes the currently animatable item and returns a collection of animators that can animate all of the animations applied to the current animatable item.  Then I loop around the animators and call animate on each one.  For now obviously I only have one item animator the RotationAnimator.  This class simply checks the direction of the item to see if it is currently being rotated.  If it is then it checks the direction and either increments or decrements the angle by the amount defined in the constants class.  Defining the amount in the constants easily allows me to tweak the animation speed.  If we are incrementing the angle and we head above 0 then we set it to 0 and set the direction to none and vice versa if we are decrementing the angle.

Next we have to update the SquareRotation class so that the left and right methods also set the direction and angle of rotation.  So when the user rotates left it sets the direction to anti-clockwise and the angle to 90 degrees.  Obviously we need to update the SquareRotator unit tests to check this.

Now that we have all of those pieces in place it is simply a matter of calling them once per frame and voila we have animations.  I have moved all of the code for animating and drawing the items into the AnimationEngine class.  This provides a nice clean wrapper for getting all of the animatable items, applying all of the animations and then finally drawing them all.  It also helps to keep the code in the game class nice and clean.

The game is starting to take shape.  If you want to get the latest version of the code then simply get the latest version from the github repository and checkout the part10 branch.  For details of how to do that see this page.