iOS在重复动作中更改SKAction速度

Question

I've read in a few placing that changing the speed variable of an SKAction will change the speed; however, that doesn't seem to be working for me.

- (void)startAnimating {
    SKAction *moveDown = [SKAction moveByX:0 y:-[CAUtilities screenSize].height duration:self.animationDuration];
    [self setMoveDownAction:[SKAction repeatActionForever:moveDown]];
    [self runAction:self.moveDownAction];
}

- (void)incAnimationSpeedBy:(CGFloat)aFloat {
    self.moveDownAction.speed += 0.5;
    NSLog(@"%f", self.moveDownAction.speed);
}

The actual value of self.moveDownAction.speed changes as seen in the NSLog call, but the actual animation doesn't change.

I have incAnimationSpeedBy: being called when the screen is tapped, so using a SKAction sequence with a runBlock won't work for my needs.

I've tried:

• Having the initial moveDown as an instance variable.
• Having the repeat forever action as an instance variable (seen above).
• Changing the duration property rather than speed .

Any help is appreciated, thanks.

Answer 1

The problem was I was trying to change the speed on the different SKAction objects when I should have been changing the speed on the parent SKSpriteNode .

- (void)startAnimating {
    SKAction *moveDown = [SKAction moveByX:0 y:-[CAUtilities screenSize].height duration:3.0];
    [self runAction:[SKAction repeatActionForever:moveDown]];
}

- (void)incAnimationSpeedBy:(CGFloat)aFloat {
    if (self.speed + aFloat < kMaxSpeed)
        self.speed += aFloat;
}