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iOS Build a Game with Sprite Kit Actions and Animations Shooting Projectiles using SKAction: Part 1

J R
J R
2,037 Points
Posted by J R
J R
2,037 Points

SpaceCat child

Hello, can someone help me to understand the difference between these two pieces of code that are in the GamePlayScene.m

  1. SpaceCatNode *spaceCat = [SpaceCatNode spaceCatAtPosition:CGPointMake(machine.position.x , machine.position.y-2)]; [self addChild:spaceCat];

  2. SpaceCatNode spaceCat = (SpaceCatNode) [self childNodeWithName:@"spaceCat"]; [spaceCat performTap];

I understand the first one is added to create the spaceCat in the view, however, the 2nd I don't understand why do we need to create a local variable inside " shootProjectileTowardsPosition".

1 Answer

Adrian Clinansmith
Adrian Clinansmith
4,379 Points
Adrian Clinansmith
Adrian Clinansmith
4,379 Points

The first line instantiates a spaceCat object just like any other alloc init or convenience constructor

The second line searches the receiver (which is self) to see if it has any children with the name "spaceCat". If a child is found it will call performTap.

We do this so that both variables are pointing to the same instance of spaceCat. There is only one spaceCat on screen, therefore instantiating multiple spaceCats will cause issues.