我有以下代码用于缓存我从Flickr加载到设备内存中的照片:NSURL*urlForPhoto=[FlickrFetcherurlForPhoto:self.photoformat:FlickrPhotoFormatLarge];NSString*rootPath=[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES)objectAtIndex:0];NSString*imagePath=[rootPathstringByAppendingString:[self.photoobjec