swift - 解决 iPhone 处理器过载时的队列问题

Question

我正在尝试将队列与核心数据结合起来。执行该函数后，处理器的利用率达到 99% 并保持不变。如果我不使用队列，处理器不会进入超速状态并返回到 1%。为什么？队列出了什么问题？

      func addGalleryPhotoToCoreDataFromImage(image: UIImage) 
  {
   dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0)) { () -> Void in
        // create a thumbnail and a smaller photo

        let thumbnailImage = self.resizeImage(image, targetSize: CGSizeMake(167, 167))
       let screenSize : CGSize = UIScreen.mainScreen().bounds.size
       let bigImage = self.resizeImage(image, targetSize: CGSizeMake(screenSize.width, screenSize.height))

        // save thumbnail and photo to CoreData
       let newPhoto = NSEntityDescription.insertNewObjectForEntityForName("Photo", inManagedObjectContext: self.managedObjectContext!) as! Photo
       newPhoto.thumbnail = UIImageJPEGRepresentation(thumbnailImage, 0.1)
       newPhoto.photo = UIImageJPEGRepresentation(bigImage, 0.9)
       self.photoSet!.addObject(newPhoto)
        self.saveToCoreData()
       dispatch_async(dispatch_get_main_queue(), { () -> Void in
           self.refreshItemsInGalleryCollectionView()
        })
      }
  }

Answer 1

将保存到coredata的代码放入主队列中