如何重复此动作3或2次而不是永远重复
SKLabelNode *label = [SKLabelNode labelNodeWithFontNamed:@"AmericanTypewriter-Bold"];
label.text = @"Boom";
label.fontColor = [SKColor blackColor];
label.fontSize = 90;
label.position = CGPointMake(CGRectGetMidX(self.frame),CGRectGetMidY(self.frame)+25);
SKAction *disappear = [SKAction fadeAlphaTo:0.0 duration:0.2];
SKAction *appear = [SKAction fadeAlphaTo:1.0 duration:0.2];
SKAction *pulse = [SKAction sequence:@[disappear,appear]];
[label runAction:[SKAction repeatActionForever:pulse]];
[self addChild:label];