iOS Endless Runner Lag SpriteKit - ios

Question

I have an iOS endless runner game where the path appears from the top and scrolls down.
Here's how I do it: 2 sprites are created and when the first one disappears from the screen, I load another sprite from an image and run the same logic.
The problem: There's a small lag right after the first sprite disappears and the new one appears.
Edit: This problem only occurs when running on iPhone 5. iPhone 4 works perfectly !
Anyone have any ideas? or has run into this problem before and solved it?
if (CurrentObstacle.frame.origin.y < -self.frame.size.height + 10) {
// clear old obstacle
CurrentObstacle = nil;
CurrentObstacle = nextObstacle;
currentObstacleImage = nextObstacleImage; // for pixel processing stuff
[self generateObstacle];
}
- (void)generateObstacle{
// genrate random image name
int i = rand()%10+1;
NSString *imageName = [NSString stringWithFormat:#"ob%i", i];
CGSize screenSize = [[UIScreen mainScreen] bounds].size;
if(screenSize.height == 480)
{
//Load 3.5 size
imageName = [imageName stringByAppendingString:#"small"];
}
imageName = [imageName stringByAppendingString:#".png"];
// create obstacle
nextObstacle = [SKSpriteNode spriteNodeWithImageNamed:imageName];
nextObstacleImage = [imageDictionary objectForKey:imageName];
nextObstacle.size = self.size;
nextObstacle.position = CGPointMake(self.view.center.x, 1.48*nextObstacle.size.height);
// set speed to be the same as the other obstacles
nextObstacle.speed = CurrentObstacle.speed;
// show obstacle
[self addChild:nextObstacle];
// move obstacle
SKAction *moveAction = [SKAction moveByX:0 y:-2*self.size.height-1 duration:8];
[nextObstacle runAction:moveAction];
}

Answer 1

Ok, solved this problem by removing the #2x images. Apparently processing big images was the cause of the lag.
Hope this helps someone!

Answer 2

You shouldn't load the image each time you want to add an obstacle. You should do a methode like this that you would call at "initWithSize"
//MyScene.h
#interface MyScene : SKScene{
SKTexture * textureObstacle1;
SKTexture * textureObstacle2;
//...//
}
-(id)initWithSize;
-(void)LoadSprites;
#end
//MyScene.m
#implementation MyScene
-(id)initWithSize:(CGSize)size {
if (self = [super initWithSize:size]) {
[self LoadSprites];
}
return self;
}
-(void)LoadSprites{
textureObstacle1=[[SKTexture alloc] initWithImageNamed:#"obstacle1.png"];
//...//
}
- (void)generateObstacle{
//...//
nextObstacle = [SKSpriteNode alloc]init];
[nextObstacle setTexture:textureObstacle1];
}
#end