[Solved] Could somebody explain the SpriteIndex -1 to me please?

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#1

I know it works but i don’t understand why it works.

In the lecture around 5mins 22secs Ben says that the SpriteIndex starts counting at 0 so we need this to be -1. However wouldn’t this imply that the index would go from Element 0 to a theoretical Element -1. So logically (at least in my head) shouldn’t this be +1 in the script instead?

Also as this Index starts counting at 0 like Ben said, why aren’t the 2 and 3 hit bricks coming into the game with the 1 hit damaged sprite that is in the Element 0 slot?
I know the LoadSprites method isn’t used until collision to change anything so this might be why but its still confusing to me.

#2

Arrays start counting at zero or in other words their index starts at zero. So an array with size = 3 or 3 items in it has:
element 0
element 1
element 2
you acces the first element in the array with an index value of 0

we assign a sprite to each of these array slots or elements.
At start the brick has not been hit yet so timesHit = 0. If i understand your confusion correctly, it’s this line in the LoadSprites() method that is getting you:
int spriteIndex = timesHit -1;
It is setting the index before we load a new sprite so we know which one to load from the sprite array.

This method won’t actually get called until the first time a block gets hit and we enter the OnCollisionEnter2D() method. timesHit gets incremented, so on the first hit it is now equal to 1 (timesHit = 1). If this isn’t a block that gets destroyed after only one hit then we call the LoadSprites() method. Now the spriteIndex gets calculated and since timesHit = 1, the index ends up being zero (spriteIndex = 1 - 1 = 0) and we access the first element in our array, Element 0. spriteIndex will never be equal to -1 and access an element outside of the bounds of the array.

I hope that helps and isn’t too confusing.

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#3

Hi Josh,

Please accept my apologies for such a late reply, my internet has been very bad for the last few weeks and i have been unable to study.

So in noobish terms as i understand; the Loadsprites method is called upon a hit. The calculation to load the sprite is the “times hit -1” so as we are starting with 1 it loads element 0 which is the first damaged brick sprite.

Thank you so much for your explanation, really appreciate you taking the time to help me out.

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