ios - 如何使警报操作无标题

<分区>

我想从警报操作中删除标题部分。制作标题字符串 "" 不会删除标题部分

@IBAction func addImage(sender: AnyObject!) {

    let alert:UIAlertController = UIAlertController(title: "" ,message: nil, preferredStyle: UIAlertControllerStyle.ActionSheet)

    let cameraAction = UIAlertAction(title: "Take Photo", style: UIAlertActionStyle.Default)
        {
            UIAlertAction in
            self.openCamera()
    }
    let gallaryAction = UIAlertAction(title: "Choose Photo", style: UIAlertActionStyle.Default)
        {
            UIAlertAction in
            self.openGallary()
    }
    let cancelAction = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.Cancel)
        {
            UIAlertAction in

    }

    // Add the actions
    alert.addAction(cameraAction)
    alert.addAction(gallaryAction)
    alert.addAction(cancelAction)

    // Present the controller
    self.presentViewController(alert, animated: true, completion: nil)

}

这是我得到的: