SKAction scaleBy: duration: SpriteKit

Question

I have a trouble trying to make one circle big and small using [SKAction scaleBy: duration:]

SKAction *scaleDown = [SKAction scaleBy:0.2 duration:1.8];  
SKAction *scaleUp= [scaleDown reversedAction];
SKAction *fullScale = [SKAction sequence:@[scaleDown, scaleUp, scaleDown, scaleUp]];
[_circleChanging runAction:fullScale];

What I get is the circle becoming so small that disappears and then doesn't come back. It has to become small and then come back to his original size doing it 2 times.

Answer 1

Try:

  SKAction *scaleDown = [SKAction scaleTo:0.2 duration:0.75];
       SKAction *scaleUp= [SKAction scaleTo:1.0 duration:0.75];
       SKAction *fullScale = [SKAction repeatActionForever:[SKAction sequence:@[scaleDown, scaleUp, scaleDown, scaleUp]]];
       [_circleChanging runAction:fullScale];

Answer 2

Not all actions are reversible, and the reverse sometimes doesn't mean "go back to the original value".

If you check the documentation, the reverse action of scaleBy is actually scaling to -0.2 in your case. Just create a new scale action instead of reversing.

Also try making a copy of the actions for the 2nd use:

SKAction *fullScale = [SKAction sequence:
                       @[scaleDown, scaleUp, [scaleDown copy], [scaleUp copy]]];