How to make a dynamic hangman game in Flash 8 with XML and ActionScript — part 5

ActionScript code that makes up the main hangman game functionality

60. Paste this ActionScript code right after the one inserted so far:

Now that is one loooong function! Don't be afraid of it :). I will show you step by step what each of this function's parts does and how it works. Before starting, just know that this function is also called once the player has pressed the "Play!" button.

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Creating a new movie clip instance from scratch

The first code inside the function that gets executed are three lines:

this.createEmptyMovieClip("allLetters_mc", 1);
allLetters_mc._y = 300;
allLetters_mc._x = 20;

The first one creates a new movie clip from scratch. The keyword this means that the movie clip will be created on the main or _root timeline, since the keyword itself resides inside the placeLetters function which is placed on the main timeline.

The createEmptyMovieClip command creates, well, an empty movie clip :). It has two parameters which must be defined: the Instance name of the new movie clip called allLetters_mc (without it, you wouldn't be able to do anything with it) and the depth at which it is stored. The depth is like a third imaginary dimension on the computer's screen. The higher the number, the more "closer to you" and further "away from the screen" the movie clip will be placed. The main timeline is on depth 0 (zero). So by choosing 1 as depth value fro your new movie clip is fine.

The next two lines place this new movie clip on new coordinates — 300 pixels from the top of the stage (_y = 300) and 20 pixels to the right of the stage's left edge (_x = 20). You have to move this movie clip so that its contents (which will come in a moment) do not overlap with the main text field (guessWord_txt).

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Placing the letter buttons on the stage

Now comes the main for loop which makes up the biggest part of the placeLetters function. Everything except the above three lines of code is placed inside it.

for (var i:Number = 0; i<alphabet.length; i++) {

Just as the previous for loops, this one starts with i set to zero, which is incremented by 1 at each pass of the loop. The condition that must be fulfilled in order for the loop to exist is that i must be lesser than the number of characters found in the alphabet variable. As you remember, you made this variable at the beginning, like this:

var alphabet:String = "abcdefghijklmnopqrstuvwxyz";

This is a String (text) variable, which holds inside all the letters of the English alphabet. So the loop will make as many iterations as there are letters in the alphabet (26). This makes perfect sense, because you must write the code that will place a button for each alphabet letter on the stage.

And here is the code that places the letter buttons on the stage:

var newLetter:MovieClip = allLetters_mc.attachMovie("letterButton", "letter"+alphabet.charAt(i), i);
newLetter.letter_txt.text = alphabet.charAt(i);
if (i<8) {
newLetter._y = 0;
newLetter._x = i*40;
} else if (i>=8 && i<16) {
newLetter._y = 40;
newLetter._x = (i-8)*40;
} else if (i>=16) {
newLetter._y = 80;
newLetter._x = (i-16)*40;
}

The first line serves attaches a movie clip dynamically from the Library onto the stage:

var newLetter:MovieClip = allLetters_mc.attachMovie("letterButton", "letter"+alphabet.charAt(i), i);

On the left side of the assignment operator (=) is the already familiar variable definition which is here, of course, of the MovieClip type. Then, you tell Flash to attach a movie clip from the Library to the empty movie clip that you have just made previously (allLetters_mc.attachMovie). This is done by first stating the Identifier name of the movie clip in the Library: letterButton in this case. You have defined this identifier when you created the small movie clip before. It is the one with the small dynamic text field inside. Here is the image of this movie clip, to avoid any confusion:

After that comes the new Instance name of the movie clip, created dynamically: "letter"+alphabet.charAt(i). This must be done like this in order to have a different Instance name for each letter button. Since the main loop makes as many passes as there are letters in the English alphabet (26), each movie clip attached from the Library will have a unique name, associated with the letter it represents. At the first iteration of the loop, when i equals zero, you will obtain the following result:

"letter"+alphabet.charAt(i)
"letter"+a
lettera

Then letterb, letterc, etc. This is thanks to the charAt() method of the String object. The variable alphabet (which contains all the letters of the alphabet) is a String. The charAt() method finds and reads the character situated at the position written between the parenthesis. In this case, this is i, meaning it is different at each iteration of the loop — so every letter of the alphabet will be read and the unique Instance name made from it.

The last parameter of the attachMovie() method is the depth of the movie clip pulled from the Library. This is again the variable i. This tells you that the depth of each movie clip will be unique. Which is excellent, because if you'd attach each movie clip on the same depth level, the previous one would get erased. There can be only one movie clip instance present on each depth level, on the location where you are attaching them. In this exercice, you are attaching all these movie clips inside the allLetters_mc movie clip which was made from scratch. Inside it, you can place as many movie clips as you like, as long as each one of them has its own unique depth level. But, imagine that you had another movie clip which would get attached ones from the Library. In it, you could again attach them using the same depth levels (0, 1, 2, 3, etc) because this would have no influence whatsoever on the first movie clip. Each movie clip is like a small world which can within itself host many other movie clips.

OK. During each iteration of the loop, a movie clip gets attached and receives its unique Instance name. And it is stored inside the newLetter variable. This is done so that during each iteration you can just reference this newly attached movie clip by telling Flash newLetter, instead of typing the whole thing, which is different each time. This simplifies your ActionScript coding greatly and makes life a lot more easier.

The next line makes the appropriate letter appear in the dynamic letter_txt text field inside each movie clip:

newLetter.letter_txt.text = alphabet.charAt(i);

Now comes an if/else if conditional statement:

if (i<8) {
newLetter._y = 0;
newLetter._x = i*40;
} else if (i>=8 && i<16) {
newLetter._y = 40;
newLetter._x = (i-8)*40;
} else if (i>=16) {
newLetter._y = 80;
newLetter._x = (i-16)*40;
}

This one serves to place the letter buttons (they act as buttons, but they are movie clip symbols, of course) on the stage in three separate rows. The first eight buttons (i<8) will be placed in the first row:

if (i<8) {
newLetter._y = 0;
newLetter._x = i*40;

That's because the _y property (vertical position) is the same: 0. The horizontal coordinate (_x) is always different: it is the result of i (0, 1, 2, 3, etc) being multiplied by 40. Why 40? Because the letter button movie clip which gets attached from the Library is 31 pixels wide. So by choosing 40 you leave 9 pixels of space between each button. The next portion of letters (i>=8 && i<16) goes in the second row, below the first one, by setting the _y property of each movie clip here to 40:

} else if (i>=8 && i<16) {
newLetter._y = 40;
newLetter._x = (i-8)*40;

The _x property is made by first substracting 8 from i and then multiplying the result by 40. If you don't substract this, the movie clips would be placed further to the right, away from the first row.

And here's the rest, following the same placement principles:

} else if (i>=16) {
newLetter._y = 80;
newLetter._x = (i-16)*40;
}

Thanks to the if conditional statement, the final result looks like this:

The movie clips containing all the letters of the alphabet are neatly arranged.

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Making the buttons clickable

Let me show you now how the buttons are made clickable via ActionScript (you already pasted this code, don't do it again :)):

newLetter.onRelease = function() {
var matchFound:Boolean = false;
var clickedLetter:String = this._name.charAt(this._name.length-1);
for (var j:Number = 0; j<chosenWord.length; j++) {
if (chosenWord.charAt(j) == clickedLetter) {
_root.guessWord_txt.text = displayedText.substr(0, j)+clickedLetter+displayedText.substr((j+1));
matchFound = true;
this._visible = false;
}
displayedText = _root.guessWord_txt.text;
}
if (displayedText == chosenWord) {
endOfGame(true);
}
if (matchFound == false) {
this._visible = false;
_root.hangman_mc.nextFrame();
if (hangman_mc._currentframe == 10) {
endOfGame(false);
}
}
};

As you can see, all the function's code is included within each attached movie clip's onRelease event. This event happens when the player press and releases the mouse button over a movie clip. If you want, you can replace this with the onPress event, which happens the instant the mouse button is pressed over the movie clip. But this latter event is best used when something has to happen quick, like a spaceship firing a shot in a shoot 'em up kind of game.

Inside the function, the first two lines are these:

var matchFound:Boolean = false;
var clickedLetter:String = this._name.charAt(this._name.length-1);

First, the matchFound variable is created, which will be later used to check if the player has clicked on a letter that is inside the hidden word. It is set to false at the beginning. Now you have to make Flash know which letter the player has clicked. To do this, you have to create a String variable which will store the clicked letter: var clickedLetter:String. After that, you retrieve the clicked letter from the movie clip's Instance name:

this._name.charAt(this._name.length-1)

The construct this._name refers to the Instance name of the movie clip that has been clicked. The ActionScript keyword this refers to the clicked movie clip because it is placed inside its onRelease event handler. After that, you use the charAt() method to extract the appropriate character/letter. Suppose the current movie clip is for example buttone. Flash would extract the letter e like this:

this._name.charAt(this.name.length - 1)
this._name.charAt("lettere".length - 1)
this._name.charAt(7 - 1)
this._name.charAt(6)
e

The length of the Instance name lettere is 7 characters. The first character in a string always has the position set to 0 (zero). That's why by substracting 1 from 7 you get 6, which is the position of the last character in the string, which is e in this case. And that character gets stored inside the clickedLetter variable.

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Using ActionScript to find a matching letter inside a word

Now comes a new for loop:

for (var j:Number = 0; j<chosenWord.length; j++) {
if (chosenWord.charAt(j) == clickedLetter) {
_root.guessWord_txt.text = displayedText.substr(0, j)+clickedLetter+displayedText.substr((j+1));
matchFound = true;
this._visible = false;
}
displayedText = _root.guessWord_txt.text;
}

Here, a new variable, j, is used, to avoid any conflict with the previous i in the main loop. It is this for loop that is checking if the clicked letter can be found anywhere in the hidden word that has to be guessed. To accomplish that, the loop must pass through all the letters of the word (to be programatically correct, all the characters of the string). That's why the condition of the loop is: j < chosenWord.length. The variable j will increase until it reaches the length (of characters) of the hidden word, the one that is stored inside the chosenWord varaible.

The loop checks if the clicked letter is inside the hidden word with the help of an if conditional statement:

if (chosenWord.charAt(j) == clickedLetter) {

This literally tells Flash:

if (the character at position j inside the string chosenWord equals the clickedLetter) {
...execute the following actions...
}

REMEMBER The equality operator (==) checks if two values are equal, while the assignment operator (=) is used to assign values to variables.

And this check is done for each character of the string stored in the chosenWord variable. If a match is found, the following three lines of code get executed:

_root.guessWord_txt.text = displayedText.substr(0, j)+clickedLetter+displayedText.substr((j+1));
matchFound = true;
this._visible = false;

The left side of the first line clearly tells you that you are commanding Flash to display some text in the guessWord_txt text field. And what will be displayed? The found letter (if the player guessed correctly), along with the all the other hidden letters, that are represented by dots (or question marks, if you decided so), that have yet to be guessed:

displayedText.substr(0, j)+clickedLetter+displayedText.substr((j+1));

On the previous page, you have set the value of the displayedText variable to dots only — the number of which equals the number of the letters inside the hidden word. Suppose the hidden word that has to be guessed is "penguin". This word is composed of 7 letters, so in this case the value of displayedText variable would be ".......". Also, suppose that the player has clicked on the letter g.

The loop would begin, making 3 iterations without finding a match. On the fourth iteration, the match would be found, because the letter g is on the position number 3 inside the word "penguin" (remember, the characters in a string are numbered beginning from zero, that's why the fourth position in a string equals number 3). The if condition would evaluate as true, and the code inside it would execute, and Flash would interpret like this:

displayedText.substr(0, j) + clickedLetter + displayedText.substr((j+1))
".......".substr(0, 3) + "g" + "......." .substr((3+1))
"..." + "g" + "..."
"...g..."

And that's what would the user see appear in the text field. Let me explain you this string manipulation in more detail. The substr() method of the String object does this: it extracts a substring from a string (i.e. a part of text), based on the starting position and length that you provided. The easiest way to understand this is by seeing an actual example.

Let's say that the word you are tinkering with is "computer", and that you wanted to extract the first three letters from it. You would do it like this:

var myText:String = "computer";
var myChunk:String = myText.substr(0, 3);

The value of the myChunk variable would be "com", which are indeed the first three characters inside the myText string. So, the first parameter between the parenthesis is the starting place inside the string, where the extraction will begin. The second parameter is the length of the string that you want to extract, including the first character. Here is a nice visual representation of that:

The functionality of the ActionScript substr method.

If you wanted to extract the text "mput", you would write substr(2, 4), because the letter m is situated at position 2 and the length of the string that you want to extract is 4. Allright!!! :-)

In the actual mechanism that writes the guessed letter along with the dots, you use this simple but very useful method to extract the first part of the word (represented by dots), before the guessed character:

displayedText.substr(0, j)

...after which you add the guessed character:

displayedText.substr(0, j) + clickedLetter

...and then you add the remaining part of the word, represented by dots, because those letters haven't been guessed yet:

displayedText.substr(0, j) + clickedLetter + displayedText.substr((j+1))

You have certainly noticed that the substr() method is used differently in this last part. There is no second parameter here: displayedText.substr((j+1)). The first one is the point where the extraction will start. And since the second one (length) is omitted, Flash will automatically pick all the characters that are found after the starting point. The starting point is exactly the character after the guessed one: j+1. In this way, the rest of the word is extracted.

Finally (whew! :-)), the lines that get executed after this string manipulation is over are:

matchFound = true;
this._visible = false;

The variable matchFound is set to true so that you can later tell Flash not to advance the hangman animation, because the player has actually guessed a letter. And the line this._visible = false hides the clicked letter. You must do this, whether the user has guessed the letter or not. You can't be cruel and make the player commit the same mistake twice, possibly. All the letters that are clicked must be eliminated, leaving only the ones that haven't been tried by the player.

And after the if conditional statement, no matter if a matching letter was found or not, the displayedText variable has to be updated:

displayedText = _root.guessWord_txt.text;

It will now reflect the current state of the guessWord_txt text field, with both the hidden and revealed letters. This is done so that a proper check can be made, to see if the whole word was guessed by the player. And that's precisely what comes next:

if (displayedText == chosenWord) {
endOfGame(true);
}

This simple if statement checks to see if the string inside the displayedText variable matches the one stored in the chosenWord variable. If it does, the endOfGame() function is called, with a Boolean true parameter passed to it, signaling that the player has won the game. That function comes later in the code, so I will not explain it now.

Some other code has to be explained now, so please continue to the next page of this tutorial to see it.

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How to make a dynamic hangman game in Flash 8 with XML and ActionScript — part 5

ActionScript code that makes up the main hangman game functionality

Creating a new movie clip instance from scratch

Placing the letter buttons on the stage

Making the buttons clickable

Using ActionScript to find a matching letter inside a word