How do I attach a node with another node? - ios

Question

I am having trouble trying to create platforms alongside a invisible line that is in the middle, I want it to have an SKPhysicsBody so that when passed through by the Hero Character, it increases the score, yet I can't seem to imagine the code the would work, specifically how to create the line with it being in the middle of the platform at all times, especially when the platform decides to move. Any tip would be greatly helpful.
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Answer 1

This is one way to implement what you described.
- (void) didMoveToView:(SKView *)view
{
// Show outline of physics bodies for debugging purposes.
self.view.showsPhysics = YES;
self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:self.frame];
self.backgroundColor = [SKColor colorWithRed:0.15 green:0.15 blue:0.3 alpha:1.0];
SKSpriteNode *platform = [SKSpriteNode spriteNodeWithColor:[SKColor blueColor] size:CGSizeMake(128, 64)];
platform.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:platform.size];
platform.position = CGPointMake(CGRectGetMidX(self.frame),
CGRectGetMidY(self.frame));
[self addChild:platform];
SKSpriteNode *line = [SKSpriteNode spriteNodeWithColor:[SKColor redColor] size:CGSizeMake(2, 128)];
// Line is invisible
line.hidden = YES;
// physicsBody of line
line.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:line.size];
// Position line...adjust this accordingly
line.position = CGPointMake(platform.position.x, platform.position.y+line.size.height/4);
[self addChild:line];
// Connect nodes with physics joint
[self connectNode1:platform toNode2:line];
[platform.physicsBody applyImpulse:CGVectorMake(100.0, 0)];
}
This method connects two sprite nodes, at their midpoint, with a physics joint.
- (void) connectNode1:(SKSpriteNode *)node1 toNode2:(SKSpriteNode *)node2
{
CGPoint midPoint = CGPointMake((node1.position.x + node2.position.x)/2,
(node1.position.y + node2.position.y)/2);
SKPhysicsJointFixed *joint = [SKPhysicsJointFixed jointWithBodyA:node1.physicsBody
bodyB:node2.physicsBody
anchor:midPoint];
[self.physicsWorld addJoint:joint];
}

Answer 2

Make the line a child of the object using the - (void)addChild:(SKNode *)node as referenced in the SKNode Class Reference.
If you do not want a child/parent relationship you can tie the line to the object like this:
line.position = CGPointMake(object.position.x+10, object.position.y+10)
where +10 is any value you need it to be. If the 'object' moves you will have to update the line's position during the update: method to keep track with the object's position.