In the last lesson you added the ability to keep track of the score. In order for the score to be useful it needs to be used in the shooter game. Today, you will make changes to make the score work with your shooter game.
1. Create the new method below for your Score class.
displayPoints
self
string: points printString
fontName: #Atlanta
size: 22
2. The method displayPoints is what will actually be used to display the score on the shooter game screen. Look at each line of code and see if you can figure out what it might be doing.
3. You will want your score to update every time points are added. Make the following change to Score>>points: to do this.
points: anInteger
points := points + anInteger.
self displayPoints
4. Now add the changes to Score>>initialize.
initialize
super initialize.
points := 0.
self lock.
self textColor: Color green.
self displayPoints.
self extent: 90 @ 0
5. These changes will set the color of the text, display the points for the screen, and set how much space the score will take up on the screen. The “lock” message keeps someone from being able to edit (type over) the score.
6. Now that your score object is ready to be used, let’s make it a part of ShooterGame. Like you did for the Ship object instance, you will also want to add an instance variable for your Score object instance. Instead of adding the score instance variable to the class code, let’s have Smalltalk add the instance variable to the code for you when you save the ShooterGame>>initializeScore method below. Note that a window will popup saying “Unknown variable: score!” since it does not yet exist. Select “declare instance” to let Smalltalk know how you want to use score in the code below.
initializeScore
score := Score new.
score position: self position + (10 @ 10).
self addMorph: score
7. Whenever a new shooter game is started, you will want the score object to be included. Adding the following change to ShooterGame>>initialize will create an instance of score for use in the game.
initialize
super initialize.
self position: 100 @ 100.
self extent: 640 @ 480.
self color: Color black.
self setNameTo: 'Shooter Game'.
self initializeShip.
self initializeScore.
self initializeEnemies
8. You can test your code by using explore morph on your running shooter game. Remember to select ShooterGame before sending these messages.
self initializeScore.
score points: 100.
9. Test your score by adding points to your score display. Send the points: message to score a number of times. What do you notice?
10. Now try sending the message “score points: -100.” What do you notice? What might this be useful for?
11. Try shooting a few enemies. What happens with the score? Why?
12. What else needs to be done for your shooter game?
13. Save and Quit your Smalltalk image.