OOP Pong

BlitzMax Forums/BlitzMax Beginners Area/OOP Pong

po	(Posted 2006) [#1]

I've been using John J's awesome OOP tutorial: http://www.blitzbasic.com/Community/posts.php?topic=59233
To try and understand OOP better, I dicided to make OO pong. Here is my code thus far:

SuperStrict	

Graphics 800,600,0,60

SeedRnd MilliSecs()

Local obj1:paddle=paddle.Create(0,265,4,True)
Local obj2:paddle=paddle.Create(790,265,4,False)
Local obj3:ball=ball.Create(395,295,1)
Local obj4:background=background.Create()

While Not KeyHit(KEY_ESCAPE)

	Local ent:entity
	For ent=EachIn entity.EntityList
		ent.Draw()
	Next		

	Flip;Cls

Wend

End

'TYPES

Type entity
	
	Field x#,y#
	
	Global EntityList:TList=New TList
	
	Method Draw() Abstract
	
	Method New()
		EntityList.AddLast(Self)
	End Method
	
End Type

Type paddle Extends entity

	Field sp#,cpu:Int,score:Int	

	Method Draw()
	
		SetColor(255,255,255)
		DrawRect(x,y,10,75)
		
	End Method
	
	Method New()
		sp#=4
		cpu=0
	End Method
	
	Function Create:paddle(x#,y#,sp#,cpu:Int)
		Local ent:paddle=New paddle
			ent.sp#=sp#
			ent.x#=x#
			ent.y#=y#
			ent.score=0
		Return ent	
	End Function
		
End Type

Type ball Extends entity

	Field sp#,dirx#,diry#

	Method Draw()
	
		SetColor(255,255,255)
		DrawRect(x,y,10,10)
		
	End Method
	
	Method New()
		sp#=1
	End Method
	
	Function Create:ball(x#,y#,sp#)
		Local ent:ball=New ball
			ent.sp#=sp#
			ent.x#=x#
			ent.y#=y#
		Return ent
	End Function
	
End Type

Type background Extends entity	

	Method Draw()
	
		SetColor(255,255,255)
		DrawRect(0,0,800,10)
		DrawRect(0,590,800,10)
		
		Local n:Int=10
		For Local i:Int=0 To 10			
			DrawRect(395,n,10,35)
			n=n+55
		Next
		
		SetScale(5,5)	
		DrawText("0",250,20)
		DrawText("0",510,20)
		SetScale(1,1)
		
	End Method	
	
	Function Create:background()
		Local ent:background=New background
		Return ent
	End Function
	
End Type

First off, does anyone see me doing anything wrong? The above code should just show a static pong game. This is where I need help though. I'm trying to get everything to update. The best place to update each type would be in each of their Draw() methods would it not? Stuff like x=x+1 and player controls. The problem is, if I put "If KeyDown(KEY_UP) Then y=y-4" inside of the paddle type's Draw() method, then it would move both of the paddles rather than just one of them moving. How do I distinguish one paddle(obj1) from the other paddle(obj2), yet keep the code in the Draw() method?

EDIT: Another thing. If I were to make a menu for this pong, would I make the menu another type which extends entity or would I just not make it a type at all?

EDIT2: You may have noticed also that in the background type's Draw() method, the scores(text) which appear on the screen are set to strings ("0"), rather than obj1.score and obj2.score. I couldn't figure out how to let those fields have access to the background type without messing up the way everything is drawn in the main loop. Any ideas?

EDIT3: Also, I put all of my types below my main loop. I just like them there(like my functions). Is there any difference between putting types above your main loop or putting them below? Or is it just personal preference?

Byteemoz

(Posted 2006) [#2]

Hi.
1) The easiest thing is to give the paddle type an "up_key" and a "down_key" field, to initialise these values when you create the type and then use them within your drawing-method:

... = paddle.Create(790,265,4,False,KEY_UP,KEY_DOWN)

...
If cpu Then
    If KeyDown(up_key) then y=y-4
    If KeyDown(down_key) Then y=y+4
End If
...

2) I'd probably use a Function that does all the drawing (background, menu-entries, cursor, ...) manages the cursor control ("If KeyDown(KEY_UP) Then cursor=cursor-1") and returns an int when the user selects an entry (1=single player, 2=multiplayer, 3=highscores, ...).

3) You could either let the paddles draw the scores or give the background type a reference to the two paddle types.

4) It's personal preference and doesn't change how your prog works.

--Byteemoz

po	(Posted 2006) [#3]

Ok, thanks for the help. I'll try all that stuff.