MyScene won't perform Action

Question

I want to perform a simple action on my Game title (zoom in/zoom out-sequence that repeats forever), but for some reason it does not work when I call the method "ZoomSequence". What is the problem with my code?

#import <SpriteKit/SpriteKit.h>
#import <AVFoundation/AVFoundation.h>

@interface MyScene : SKScene

@property (strong, nonatomic) SKLabelNode *mainTitle;

@end

#import "MyScene.h"

@implementation MyScene

@synthesize mainTitle;

-(id)initWithSize:(CGSize)size {
    if (self = [super initWithSize:size]) {
        SKSpriteNode *background = [[SKSpriteNode alloc] initWithImageNamed:@"bg.png"];
        background.anchorPoint = CGPointMake(0, 0);
        background.zPosition = 1;
        [self addChild: background];

        SKLabelNode *title = [SKLabelNode labelNodeWithFontNamed:@"Verdana-BoldItalic"];
        title.fontSize = 45;
        title.text = @"Game Title";
        title.position = CGPointMake(260, 250);
        title.zPosition = 3;
        self.mainTitle = title;
        [self addChild:title];

        [self ZoomSequence];

    }
    return self;
}

-(void)ZoomSequence{
    SKAction *HUDzoom = [SKAction scaleTo:2.0 duration:2];
    SKAction *HUDzoomOut = [SKAction scaleTo:1.0 duration:2];
    SKAction *HUDAnimation = [SKAction sequence:@[HUDzoom, HUDzoomOut]];

    [self.mainTitle runAction:[SKAction repeatActionForever:HUDAnimation]];
}

Answer 1

Fixed it. It needed one touch on the Screen for the action to start, but I did not notice that, because my Level1-Scene was always opened on the first touch and MyScene was dismissed:

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    SKScene *firstLevel = [[Level_1 alloc] initWithSize:self.size];
    [self.view presentScene: firstLevel];
}

so I modified my method like this:

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    if (firstTouch == YES){
        firstTouch = NO;
    }else if (firstTouch == NO){
    SKScene *restart = [[Level_1 alloc] initWithSize:self.size];
    [self.view presentScene:restart];}
}