How can i make a node collide with the sides of moving scene?

Question

Hi i wish to know how can my nodes can collide with a moving scene. I have a main node that cans move along the x axis and cans collide with other nodes. I want to make the non main nodes collide with the sides of the moving scene. How can i make that ? ( the camera only follow the main node).

I have an obstacle class.

in my MLObstacle.m

-(id)init
{
if(self = [super init])
{
int aux = arc4random()%3;
switch (aux) {
    case 0:
        self = [MLObstaculo spriteNodeWithColor:[UIColor greenColor] size:CGSizeMake((aux+1)*10,(aux+1)*13 )];
        break;
    case 1:
        self = [MLObstaculo spriteNodeWithColor:[UIColor blueColor] size:CGSizeMake((aux+1)*10,(aux+1)*15 )];
        break;
    case 2:
        self = [MLObstaculo spriteNodeWithColor:[UIColor redColor] size:CGSizeMake((aux+1)*10,(aux+1)*14 )];
        break;
}
self.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:self.size];
self.physicsBody.affectedByGravity = NO;

self.physicsBody.categoryBitMask = obstacleCategory;
self.physicsBody.contactTestBitMask = visibleSidesCategory;
self.physicsBody.collisionBitMask = visibleSidesCategory;   
[self setDx:0.0];
[self setDy:2.4];
}
return self;
}

So i add Obstacles to my WorldClass

In my WorlGen.m

-(void)GenerateWorld
{
SKSpriteNode *Ground = [SKSpriteNode spriteNodeWithColor:[UIColor greenColor] size:CGSizeMake(self.scene.frame.size.width,100)];
Ground.position = CGPointMake(0, -self.scene.frame.size.height/2 + Ground.size.height/2);
Ground.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:Ground.size];
Ground.physicsBody.dynamic = NO;


[self addChild:Ground];
for(int i = 0; i < 3; i++)
{

    MLObstaculo * auxobs= [[MLObstaculo alloc]initObstaculo];
    auxobs.position = CGPointMake((i+1)*50, Ground.position.y + Ground.size.height/2 +auxobs.size.height/2 );
    [self.Obstaculos addObject:auxobs];
    [self addChild:auxobs];
    auxobs = NULL;

}
}

and then i add the world to my scene

Scene.m

-(id)initWithSize:(CGSize)size
{
     if(self = [super initWithSize:size]
     {
        WorldGen * world = [[WorldGen alloc] init];
        self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:self.frame];
        self.physicsWorld.contactDelegate = self;
        self.physicsBody.categoryBitMask = VisibleSidesCategory
        self.physicsBody.collisionBitMask = ObstacleCategory;
        self.anchorPoint = CGPointMake(0.5,0.5);
        [self addChild:world];
        [world GenerateWorld];
     }
}

Update...

-(void)didSimulatePhysics
{
    [self centerOnNode:hero];
}

-(void)centerOnNode:(SKNode *)node
{
    CGPoint pointinScene = [self convertPoint:node.position fromNode:node.parent];
    world.position = CGPointMake(world.position.x -pointinScene.x , world.position.y);

}

I initalized all the category variables with this format ( static const uint32_t ObstacleCategory = 0x1 <<1; )

Answer 1

From this and another question's problem, I have finally determined there is an error in the API. Specifically, a node's anchorPoint is considered (0,0) during initialization if using a WithRect: or FromRect: based initializer(but not a RectOfSize: or center: based one), so you get unexpected behavior.

Thus, even when the anchorPoint of the Scene and other objects are set to (0.5,0.5), a node places its lower left corner relative to the parent node's midpoint, rather than placing the child's midpoint relative to the parent node's midpoint.

Specifically, this can be solved in any one of these three ways:

1. Use an anchorPoint of (0,0).
2. Create your nodes without using Rect based initializers. You can use shapeNodeWithRectOfSize: instead of shapeNodeWithRect: and bodyWithEdgeLoopFromPath: instead of bodyWithEdgeLoopFromRect:
3. Set the Rect's initial position as lower and to the left, like so:

node.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:CGRectMake(-node.size.width/2, -node.size.height/2, node.size.width, node.size.height)];

Answer 2

First edit by defining your collisionBitMask

-(id)init
{
    self.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:self.size];
    self.physicsBody.categoryBitMask = ObstacleCategory;
    self.physicsBody.contactTestBitMask = VisibleSidesCategory;
    self.physicsBods.collisionBitMask = VisibleSidesCategory;
}

Second make this steps in Xcode -> File -> New -> File -> C and C++ -> Header File

Give a name of Physics.h and add those lines in it:

typedef enum : uint8_t {
    ObstacleCategory            = 1,
    VisibleSidesCategory        = 2,

} ColliderType;

and then import Physics.h into all your classes (You don't need to alloc or init for Physics.h, just use ObstacleCategory and VisibleSidesCategory)