Inheritance

BlitzMax Forums/BlitzMax Beginners Area/Inheritance

Steve Elliott

(Posted 2006) [#1]

I have some characters that move about, and I have a particle effect working fine in isolation.

Now I want the particles to move with the correct characters, and when the character is deleted so are the particles. I came up with the idea of using an IdNumber to associate the character with the particle set which should work fine.

But could Inheritance be used in some way to automate this process? Some simple code would be appreciated as I'm still getting used to the OOP way of things.

Dreamora

(Posted 2006) [#2]

No, inheritance is quite pointless here unless you extend the emitter from a general pivot class or similar.

Inheritance extends a given base object, thats why it isn't of much use here.

tonyg

(Posted 2006) [#3]

Allocate your particles to an 'emitter' and then assign the emitter to a field in the character type definition.

bradford6

(Posted 2006) [#4]

what Dreamora and Tonyg said.

to elaborate a little.

I do not think inheritence is the right thig to do. You might want to try a concept called 'Composition'. instead of the DERIVED type extending a BASE type, you would build your Character type from other, seperate types (i.e Compose). remember that adding Field emitter:Temitter does not instantiate an object of Type Temitter. you still have to do that with NEW.

Type Character
	Field emitter:Temitter
	
	
	Method update
		handleemitter() ' call the emitter handler
		draw()	' call the draw method and draw the character
	End Method
	
	
	Method draw
		
		' draw character
	End Method
	
	Method handleEmitter()
		pseudocode
		If its time To emit particles
			Then emitter.emit()
		EndIf
	
	End Method
	

End Type

Type Temitter
	Field x,y

	Method emit()
	' emit particles
	End Method
End Type

Steve Elliott

(Posted 2006) [#5]

Thanks for the suggestions and code.

SculptureOfSoul

(Posted 2006) [#6]

The best way to determine when to use inheritance (well maybe not best, but easiest) is to, assuming you have two objects A and B, ask yourself "Is A a type of B, or does A have a B."

So if you had two objects, TChicken and TWing, it's pretty obvious that the TChicken isn't a type of wing but instead has a wing. So "has a" relationships are best modeled through composition. "Is a" relationships are best modeled through inheritance. Given objects TChicken and TBird we can conclude that inheritance is the best modeling approach since a chicken is a type of bird.