儲存多張圖片的時候，既要控制不丟圖片，又要控制圖片可以多執行緒。提高儲存速度，防止程式崩潰，防止使用者等待時間過久

這裡我們可以使用Photos框架的PHPhotoLibrary類，這個可以幫助你多執行緒儲存圖片

-(void)saveBtn
{
      [SSGOTools againRequestPhotoWithblock:^(BOOL isAgree) {             
                if (isAgree) {                  
                    //確認開啟許可權
                    self.listOfImages = [NSMutableArray new];
                    int photoNum ;
                    photoNum = (int)_photoArray.count;
                    if (_photoArray.count > 9) {
                        photoNum = 9;
                    }
                    for (int i = 0; i < photoNum; i++) {
                        NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:_photoArray[i]]];
                        UIImage *myImage = [UIImage imageWithData:data];
                        //[self.listOfImages addObject:myImage];
                        [self loadImageFinished:myImage];
                       
                        }
                }            
            }];
}
 

- (void)loadImageFinished:(UIImage *)image
{
    [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
        
        //寫入圖片到相簿
        
        [PHAssetChangeRequest creationRequestForAssetFromImage:image];
       
    } completionHandler:^(BOOL success, NSError * _Nullable error) {
        
        NSLog(@"success = %d, error = %@", success, error);
        if(success){
            dispatch_async(dispatch_get_main_queue(), ^{
                [SSGOTools showInfoPopHint:@"儲存成功"];
            });
        }
    }];
}