将图片写入系统相册

/**
 保存图片到系统相薄
 */
- (void)saveImageToSystemPhotoLibrary
{
    NSData *data = [NSData dataWithContentsOfURL:[NSURL  URLWithString:self.listModel.originalUrls[_currentIndex]]];
    UIImage *image = [UIImage imageWithData:data]; // 取得图片
    
    [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
        //写入图片到相册
        PHAssetChangeRequest *req = [PHAssetChangeRequest creationRequestForAssetFromImage:image];
    } completionHandler:^(BOOL success, NSError * _Nullable error) {
        NSLog(@"success = %d, error = %@", success, error);
        if (success)
        {
            NSLog(@"=========保存图片成功");
        }
    }];
}

将图片写入系统相册和相薄

- (void)saveImageToPhotoLibrary
{
    NSData *data = [NSData dataWithContentsOfURL:[NSURL  URLWithString:self.listModel.originalUrls[_currentIndex]]];
    UIImage *image = [UIImage imageWithData:data]; // 取得图片
       //保存图片
       __block NSString *assetId = nil;
      // 1. 存储图片到"相机胶卷"
       [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
             // 新建一个PHAssetCreationRequest对象
             // 返回PHAsset(图片)的字符串标识
         assetId = [PHAssetCreationRequest creationRequestForAssetFromImage:image].placeholderForCreatedAsset.localIdentifier;
           } completionHandler:^(BOOL success, NSError * _Nullable error) {
                 // 2. 获得相册对象
                 PHAssetCollection *collection = [self getCollection];
                 // 3. 将“相机胶卷”中的图片添加到新的相册
                 [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
                       PHAssetCollectionChangeRequest *request = [PHAssetCollectionChangeRequest changeRequestForAssetCollection:collection];
                       NSLog(@"%@", [PHAsset fetchAssetsWithLocalIdentifiers:@[assetId] options:nil]);
                       // 根据唯一标示获得相片对象
                       PHAsset *asset = [PHAsset fetchAssetsWithLocalIdentifiers:@[assetId] options:nil].firstObject;
                       // 添加图片到相册中
                       [request addAssets:@[asset]];
                     } completionHandler:^(BOOL success, NSError * _Nullable error) {
                           NSLog(@"成功保存到相簿：%@", collection.localizedTitle);
                          [MBProgressHUD showSuccessMessage:@"保存图片成功"];
                     }];
        }];
}

 - (PHAssetCollection *)getCollection {
      // 先获得之前创建过的相册
      PHFetchResult<PHAssetCollection *> *collectionResult = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeAlbum subtype:PHAssetCollectionSubtypeAlbumRegular options:nil];
      for (PHAssetCollection *collection in collectionResult) {
            if ([collection.localizedTitle isEqualToString:@"搜缘"]) {
                   return collection;
                }
           }
    
       // 如果相册不存在,就创建新的相册(文件夹)
       __block NSString *collectionId = nil; // __block修改block外部的变量的值
      // 这个方法会在相册创建完毕后才会返回
       [[PHPhotoLibrary sharedPhotoLibrary] performChangesAndWait:^{
            // 新建一个PHAssertCollectionChangeRequest对象, 用来创建一个新的相册
             collectionId = [PHAssetCollectionChangeRequest creationRequestForAssetCollectionWithTitle:@"搜缘"].placeholderForCreatedAssetCollection.localIdentifier;
           } error:nil];
   
       return [PHAssetCollection fetchAssetCollectionsWithLocalIdentifiers:@[collectionId] options:nil].firstObject;
}