Saturday, August 10, 2019

Creating the Card Class

We will place all the code for the Card movie in an external JavaScript file. For some strange reason, Animate CC 2017 does not let you edit external JavaScript files (hopefully an over-site that will be fixed in future versions) so another editor will have to be used for editing the JavaScript file. There are numerous editors available that support JavaScript, with Notepad++ being the editor of choice for me when I am using a windows machine.

Before we can create the card class, however, we are going to want to create a separate namespace for holding our classes so that there are no conflicts with any other code that we are using. The easiest way of creating a namespace is simply to create a root object with the name of the namespace we wish to  use. This can be done as follows:

spelchan = spelchan | {};

You should already be familiar with the new operator, which is used for creating instances of a class. The format for this is

 new constructor([param1,...,paramn]);
 
What is happening is the new operator is trying to find a constructor function named whatever name was provided with the number of parameters indicated. Some constructor functions, such as Array, are built right in to JavaScript. It is, however, possible to create new Constructor functions by simply having a function named whatever it is you want to call the constructor. Convention has it that you start constructor functions with a capital letter. This is a good idea as it distinguishes them from other functions.

Constructors can have no parameters, or as many parameters as you desire. Here is the constructor function for our card class. Notice that it takes a reference to the movie clip that it will be controlling. We could have had the class create the movie clip but by passing the movie clip we make it easier to attach objects from the Animate CC editor to our class.

spelchan.Card = function(cardMovie) {
this.cardMovie = cardMovie;
this.cardID = 0;
this.faceShowing = false;
this.cardMovie.gotoAndStop(9+this.cardID);
}

As a class consists of data and the methods used to manipulate the data, the above constructor sets up a holder for the card movie, the id of the card, and a Boolean flag that indicates if the card is being shown. By default, the card is blank and is not being shown to the user. To set the card and show the card, we need to have some methods. This is where JavaScript gets kind of weird.

All classes are given a prototype object that holds functions and other variables that are available to any instance of that class. To add a function to a class, you need to add the function to the prototype object. This can be done two ways. First, you can create the function directly in the constructor by assigning the function name to the code for a function. The other way is to assign a function to the prototype, by using classname.prototype.functionname = function(...) { ... };

Let us implement the setCard and getCard methods. When the card’s value is changed, the card has to go to the proper frame of the movie and stop. However, if the card’s face is not showing, we show the back image instead. Getting the card value is simply the matter of returning the cardID variable.

// n is the cardID for the card
spelchan.Card.prototype.setCard = function(n)
{
if ((n < 1) || (n > 52))
this.cardID = 0;
else
this.cardID = n;
if ((this.cardID == 0) || (this.faceShowing == false))
this.cardMovie.gotoAndStop(1);
else
this.cardMovie.gotoAndStop(9+this.cardID);
}

// returns the cardID for the card
spelchan.Card.prototype.getCard = function()
{
return this.cardID;
}

We now have the ability to change the card but as the face is not being shown, we have no way of verifying this. Showing a card is simply a matter of setting the faceShowing variable to true and going to the appropriate frame. The only complication is the fact that we need to handle a card that has yet been assigned a value. Hiding the face is even easier as we set faceShowing to false then stop on the blank card frame.

// shows the face side of the card
spelchan.Card.prototype.showFace = function()
{
this.faceShowing = true;
if (this.cardID == 0)
this.cardMovie.gotoAndStop(1);
else
this.cardMovie.gotoAndStop(9+cardID);
}

// shows the back of the card
spelchan.Card.prototype.hideFace = function()
{
this.faceShowing = false;
this.cardMovie.gotoAndStop(1);
}

This is all that is needed for a card class, but creating a couple of utility methods for getting the face of the card and the suit of the card is easy enough to do. This is done using math. The modulus function, which uses the % operator,  gives you the remainder of a division. Had we started counting from 0, this would work great, but as we didn’t subtracting one from the card id lets us use modulus to get the face value from 0 to 12 and adding 1 corrects this. A similar technique can be used to determine which of the four suits are being used by seeing which group of 13 the card falls into.