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Abstract Types and design

BlitzMax Forums/BlitzMax Programming/Abstract Types and design

Curtastic(Posted 2006) [#1]
An abstract type means you can't make an instance of it. It's supposed to be used when you inherit. But I'm doing this:

Type FPSCounter Abstract
	Global Draws:Int
	Global DrawTime:Int
	Global FPS:Int

	Function Update()
		If MilliSecs()-drawtime>=1000 Then
			fps=draws
			draws=0
			drawtime=MilliSecs()
		Else
			draws:+1
		EndIf
	EndFunction

	Function Draw()
		SetColor 255,255,255
		DrawText "FPS: "+fps,1,1
	EndFunction
EndType


Everything works fine, except the debugger won't show the values of these globals when the program is stopped. I think it assumes you would never do what I am doing. Is doing this a bad idea? I'm just calling it abstract to show that you never make an instance of it.


Gabriel(Posted 2006) [#2]
I hope not. I do this too.


Jim Teeuwen(Posted 2006) [#3]
The debugger should show the values regardless of whether it's abstract or not. Global values have nothing to do with it since they are not restricted to an instance of the object.

I'd say that's a bug in the debugger.


Sean Doherty(Posted 2006) [#4]
Try putting your global variables outside the type.


H&K(Posted 2006) [#5]
Global values have nothing to do with it since they are not restricted to an instance of the object


I asked about this quite a long time ago, and everyone told me I was stupid for asking. But the problem is when are the Globals of a type to be initialised. Is it to be the first time an object is created (I think not, but might be), is it the first time the object is referenced, (I dont know, but would not happen for an abstract type), is it at the start of runtime, (Most people said yes to this)

Now add to this problem the fact that you have made your type abstract, and it becomes more of a problem.

@Curtastic
You havent said what you are doing, you have just shown the type, what are you doing with it? If you arent doing anything, then its probable that the gloabal simply dont exist until you do something


Curtastic(Posted 2006) [#6]
@Gabriel, Good I'm not the only one!
@Jim, I agree.
@Sean Doherty, I want everything to be inside types.
@H&K, It's just a normal frames per second counter, and the globals are definately created. Here's some better code:

Strict

Type FPSCounter Abstract
	Global Draws:Int = Test()
	Global DrawTime:Int
	Global FPS:Int

	Function Update()
		If MilliSecs()-drawtime>=1000 Then
			fps=draws
			draws=0
			drawtime=MilliSecs()
		Else
			draws:+1
		EndIf
	EndFunction

	Function Draw()
		SetColor 255,255,255
		DrawText "FPS: "+fps,1,1
	EndFunction
EndType


Graphics 555,555

Print "Main loop"

Repeat
	If KeyHit(key_escape) Then End
	fpscounter.update()
	fpscounter.draw()
	Flip
	Cls
	If MouseHit(1) Then DebugStop
Forever


Function Test()
	Print "Globals initialized"
EndFunction



H&K(Posted 2006) [#7]
Yep, my vote for a debugger problem


tonyg(Posted 2006) [#8]
I think it's a bug but don't understand what 'abstract' has to do with it. Take abstract out and you don't see the values either... or am I missing something?


Gabriel(Posted 2006) [#9]
Nope, you're quite correct. It does not place the type into the debugger at all until you create an instance, regardless of whether or not its abstract.