SpriteKit 1 Dimensional Movement

Question

I'm using apple's Sprite Kit and I need to move a SKSprite Node in horizontal movement only. I want the rest of the physics to apply but only in the horizontal component.

Context: This is for an object supposedly on a slider that can bounce back and forth. I have everything done but if it is hit the end the wrong way it simply floats off vertically, how can I simply make it ignore all forces in the vertical direction.

Answer 1

By putting the node's position back at the desired Y coordinate every frame after physics has been simulated:

-(void) didSimulatePhysics
{
    CGPoint pos = horizontalMoveNode.position;
    pos.y = fixedVerticalPosY;
    horizontalMoveNode.position = pos;
}

Add this method to your scene class and apply it to whichever node(s) you want to lock in at a given Y coordinate.