intersectsNode not working? - sprite-kit

Question

I'm trying to detect when one node overlaps another. I am teaching myself sprite kit and cannot get intersectsNodes to give any output. I've loaded 2 nodes that can be moved around on the screen and then added intersectsNodes in the update section.
-(void)update:(CFTimeInterval)currentTime {
SKSpriteNode* playerShip1;
SKSpriteNode* playerShip2;
if ([playerShip1 intersectsNode: playerShip2]) {
NSLog(#"your ships overlap");
}
Any thoughts on why no intersection is found?
here is the whole m file.
#import "MyScene.h"
#implementation MyScene
-(id)initWithSize:(CGSize)size {
if (self = [super initWithSize:size]) {
SKSpriteNode* playerShip1 = [SKSpriteNode spriteNodeWithImageNamed:#"player"];
playerShip1.position = CGPointMake(self.frame.size.width/2, playerShip1.frame.size.height);
playerShip1.name = #"PLAYER_SHIP_1";
[self addChild:playerShip1];
SKSpriteNode* playerShip2 = [SKSpriteNode spriteNodeWithImageNamed:#"player"];
playerShip2.position = CGPointMake(self.frame.size.width/2, self.frame.size.height-playerShip2.frame.size.height);
playerShip2.name = #"PLAYER_SHIP_2";
[self addChild:playerShip2];
SKSpriteNode* playerShip3 = [SKSpriteNode spriteNodeWithImageNamed:#"player"];
playerShip3.position = CGPointMake(self.frame.size.width/2, self.frame.size.height/2);
playerShip3.name = #"PLAYER_SHIP_3";
[self addChild:playerShip3];
activeDragNode = nil;
}
return self;
}
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
// Identify where this touch is on the scene
CGPoint scenePosition = [touch locationInNode:self];
// Find the child node that contains this touch
SKNode* checkNode = [self nodeAtPoint:scenePosition];
// Make sure it is a player ship and not another node like the parent SKScene
if (checkNode && [checkNode.name hasPrefix:#"PLAYER_SHIP"]) {
activeDragNode = (SKSpriteNode*)checkNode;
SKAction *zoomAction = [SKAction scaleTo:1.5 duration:.2];
[checkNode runAction:zoomAction];
//NSLog(#"your ship has been hit!");
}
}
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
// Remove reference to which object we are dragging
activeDragNode=nil;
UITouch *touch = [touches anyObject];
CGPoint scenePosition = [touch locationInNode:self];
SKNode* checkNode = [self nodeAtPoint:scenePosition];
SKAction *shrinkAction = [SKAction scaleTo:1.0 duration:.2];
[checkNode runAction:shrinkAction];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
// Be sure we have a reference to an object to drag
if (activeDragNode==nil) return;
UITouch *touch = [touches anyObject];
CGPoint scenePosition = [touch locationInNode:self];
CGPoint lastPosition = [touch previousLocationInNode:self];
// Calculate the new location of the dragged node
CGPoint newLoc = CGPointMake(activeDragNode.position.x + (scenePosition.x - lastPosition.x), activeDragNode.position.y + (scenePosition.y - lastPosition.y));
// Update this location
activeDragNode.position = newLoc;
}
-(void)update:(CFTimeInterval)currentTime {
SKSpriteNode* playerShip1;
SKSpriteNode* playerShip2;
if ([playerShip1 intersectsNode: playerShip2]) {
NSLog(#"your ships overlap");
}
/* Called before each frame is rendered */
}
#end

Answer 1

First you need to set a position for each node:
playerShip1.position = CGPointMake(0,0);
Second you need to add each node to the view:
[self addChild:playerShip1];
Also, you are adding the nodes in your update method which is the wrong place. As your code is now, you will continuously add each node 60 times a second.
I see you adding additional code. You are creating 3 SKSpriteNodes in your init method which is fine and works. However, you are not keeping a reference to these 3 nodes. This means once they are created, you have no way to access them again. To resolve this, you should create 3 SKSpriteNode class properties or add all 3 nodes into an array (class property for the array). If you don't know what I mean, that's ok, it just means you have a ways to learn.
I suggest you do a couple of tutorials as this will teach some additional fundamentals and prevent a ton of "why isn't this working" frustration in the future.