问为什么我不能将一个SKScene添加到另一个SKScene中？

EN

-(void)dieFrom:(SKNode*)killingDebris {
    _touched = YES;

    if (_touched == YES) {
        beatLevel = YES;
        NSLog(@"touched");

        [self runAction:[SKAction sequence:@[
            [SKAction runBlock:^{
            [_goodSquare removeFromParent];
        }],
            [SKAction runBlock:^{

            level2Achieved = [[NSUserDefaults standardUserDefaults] integerForKey:@"newLevelAchieved"];
            if (beatLevel == YES) {
                level2Achieved = 2;
            }
            [[NSUserDefaults standardUserDefaults] setInteger:level2Achieved forKey:@"newLevelAchieved"];
            [[NSUserDefaults standardUserDefaults] synchronize];
            [self removeAllChildren];
        }],
            [SKAction waitForDuration:1.5],
            [SKAction runBlock:^{

            [self endGame];

        }],
                                                   ]]];

    }
}

-(void)endGame {

    [self removeAllActions];

    gameOverScene *gameOverNode = [[gameOverScene alloc] initWithScore:self.score];
    gameOverNode.gameScene = self;
    gameOverNode.position = CGPointMake(self.scene.size.width/2, -150);
    [self addChild:gameOverNode];

    [gameOverNode runAction:[SKAction moveToY:self.scene.size.height/2 duration:0.6]];
}

@class testScene;

@interface gameOverScene : SKScene

@property (weak, nonatomic) testScene *gameScene;

-(instancetype)initWithScore:(NSInteger)score;

@end

-(instancetype)initWithScore:(NSInteger)score {

    if (self = [super init]) {
        self.userInteractionEnabled = YES;
        self.zPosition = 5.0;

        SKSpriteNode *bg = [SKSpriteNode spriteNodeWithColor:[SKColor redColor] size:CGSizeMake(280, 300)];
        bg.alpha = 0.6;
        [self addChild:bg];
    }
    return self;
}

2014-05-11 15:22:05.502 test2[2825:60b] SKScene: Setting the zPosition of a SKScene has no effect.
2014-05-11 15:22:05.503 test2[2825:60b] SKScene: Setting the position of a SKScene has no effect.
2014-05-11 15:22:05.504 test2[2825:60b] SKScene: Animating the position of a SKScene has no effect.