iOS 把图片存到相册中

-(void)savaPicAction{

    UIImageWriteToSavedPhotosAlbum(_imageView.image, nil, nil, nil);

    UIAlertView * alert = [[UIAlertView alloc] initWithTitle:nil message:@"保存成功" delegate:self cancelButtonTitle:nil otherButtonTitles:@"确定", nil];

    [alert show];

}