将UIImageView上的图片保存到相册中

//实现该方法
- (void)saveImageToPhotos:(UIImage*)savedImage
{
UIImageWriteToSavedPhotosAlbum(savedImage, self, @selector(image:didFinishSavingWithError:contextInfo:), NULL);
//因为需要知道该操作的完成情况，即保存成功与否，所以此处需要一个回调方法image:didFinishSavingWithError:contextInfo:
}

//回调方法
- (void)image: (UIImage *) image didFinishSavingWithError: (NSError *) error contextInfo: (void *) contextInfo
{
NSString *msg = nil ;
if(error != NULL){
msg = @"保存图片失败" ;
}else{
msg = @"保存图片成功" ;
}

UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"提示" message:msg preferredStyle:UIAlertControllerStyleAlert];
[self showViewController:alert sender:nil];
}
//注iOS9弃用了UIAlertView类。