Update SKShapeNode that is attached to SKNode - objective-c

Question

I am trying to modify SKShapeNode that I already added to SKNode.
This is my code for adding SKNode to the screen and attaching SKShapeNode to it. Now I am trying to modify color of that specific SKShapeNode, but I am not sure how to do it. Any advice?
SKNode *dot = [SKNode node];
SKShapeNode *circle = [SKShapeNode node];
circle.path = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(0, 0, 20, 20)].CGPath;
circle.fillColor = [UIColor blueColor];
circle.strokeColor = [UIColor blueColor];
circle.glowWidth = 5;
[dot addChild:circle];
[self addChild:dot];

Answer 1

try to remove all children and readd new child
[dot removeAllChildren];
[dot addChild:circle];

Answer 2

Make SKShapeNode a property of your SKScene:
#interface YourScene()
#property SKShapeNode *circle;
#end
Change the code which creates the circle to this:
self.circle = [SKShapeNode node];
self.circle.path = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(0, 0, 20, 20)].CGPath;
self.circle.fillColor = [UIColor blueColor];
self.circle.strokeColor = [UIColor blueColor];
self.circle.glowWidth = 5;
[dot addChild:self.circle];
Now you can access circle node anywhere in the scene:
- (void)changeColor {
self.circle.fillColor = [SKColor redColor];
}
Another option is to give the node a name:
SKShapeNode *circle = [SKShapeNode node];
.....
circle = #"circle";
And access that node by name
- (void)changeColor {
// Assuming the dot node is a child node of the scene
SKShapeNode *circle = (SKShapeNode*)[self.scene childNodeWithName:#"/circle"];
circle.fillColor = [SKColor redColor];
}