SpriteKit SKSpriteNode slide - objective-c

Question

I'm trying determine why slide is happened. I have created 2 nodes, and one of them is moving using SKAction. But when one of them above on other, it does not moving with node under them.
It's a little bit hard to explain, so I have created the video:
https://www.youtube.com/watch?v=F4OuTBVd5sM&feature=youtube_gdata_player
Thanks for your replies!
Parts of code:
CGPoint positionPoint = [valuePoint CGPointValue];
SKSpriteNode *slab = [SKSpriteNode spriteNodeWithTexture:plitaTexture];
slab.name = #"plita";
slab.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:plitaTexture.size];
slab.position = positionPoint;
slab.physicsBody.dynamic = NO;
CGFloat duration = 3.0;
CGFloat firstDuration = duration/(self.size.width/slab.position.x);
SKAction *moveLeftFirstTime = [SKAction moveTo:CGPointMake(0.0 + plitaTexture.size.width/2, positionPoint.y) duration:firstDuration];
SKAction *moveLeft = [SKAction moveTo:CGPointMake(0.0 + plitaTexture.size.width/2, positionPoint.y) duration:5];
SKAction *moveRight = [SKAction moveTo:CGPointMake(self.size.width - plitaTexture.size.width/2, positionPoint.y) duration:5];
SKAction *movingRightLeft = [SKAction sequence:#[moveRight, moveLeft]];
SKAction *moving = [SKAction sequence:#[moveLeftFirstTime,[SKAction repeatActionForever:movingRightLeft]]];
[slab runAction:moving];
[self addChild:slab];
Rabbit init code:
-(instancetype)init {
if (self = [super initWithImageNamed:#"eating-rabbit1"]) {
self.physicsBody = [SKPhysicsBody bodyWithTexture:self.texture size:self.texture.size];
self.physicsBody.allowsRotation = NO;
self.physicsBody.dynamic = YES;
self.physicsBody.friction = 1;
}
return self;
}

Answer 1

The main character is sliding because you are moving the slab by changing its position over time. Imagine you are standing on top of a train that is moving, friction will cause you to move along in the direction of the train. However, if the train magically moved from point A to point B by disappearing and reappearing 1 cm at a time, you will remain at point A. That is what's happening to your main character.
To correct this issue, you will need to move the slabs using physics. Here is an example of how to do that:
slab.physicsBody.affectedByGravity = NO;
slab.physicsBody.dynamic = YES;
// These will help prevent the slab from twisting due to the weight of the main character
slab.physicsBody.angularDamping = 1.0;
slab.physicsBody.mass = 1e6;
// Air resistance will slow slab's movement, set the damping to 0
slab.physicsBody.linearDamping = 0;
Define a set of SKActions that will move the slabs left and right. Adjust the speed and duration variables to achieve the desired motion.
SKAction *moveLeft = [SKAction customActionWithDuration:0 actionBlock:^(SKNode *node, CGFloat elapsedTime){
node.physicsBody.velocity = CGVectorMake(-speed, 0);
}];
SKAction *moveRight = [SKAction customActionWithDuration:0 actionBlock:^(SKNode *node, CGFloat elapsedTime){
node.physicsBody.velocity = CGVectorMake(speed, 0);
}];
SKAction *wait = [SKAction waitForDuration:duration];
SKAction *action = [SKAction sequence:#[moveRight, wait, moveLeft, wait]];
[slab runAction:[SKAction repeatActionForever:action]];

Answer 2

You need to set the slab's physicsBody to be dynamic.
slab.physicsBody.dynamic = YES;
slab.physicsBody.affectedByGravity = NO;
A non-dynamic physicsBody is rendered static and ignores any forces and impulses applied on it. Look up the property in the documentation here.