创建后如何获得指向新 PHCollectionList（或 PHAssetCollection）的指针

Posted 2023-03-10

【中文标题】创建后如何获得指向新 PHCollectionList（或 PHAssetCollection）的指针

【英文标题】：How do you get a pointer to a new PHCollectionList (or PHAssetCollection) after creating

【发布时间】：2015-08-28 21:54:06

【问题描述】：

我正在尝试创建一个照片“文件夹”并返回一个指向它的指针。这可能吗？以下是我到目前为止的代码。谢谢。

- (PHCollectionList *) CreatePhotoFolder: (NSString *) folderName

    [[phphotoLibrary sharedPhotoLibrary]
        performChanges:^
            // Create the folder
            [PHCollectionListChangeRequest creationRequestForCollectionListWithTitle: folderName];
        
        completionHandler:^(BOOL success, NSError *error) 
            if (!success)  NSLog(@"Error creating Folder: %@", error); 
            else 
                // How do I return the new PHCollectionList* for the new folder?
            
        
     ];

【参考方案1】：

需要先通过占位符获取本地ID。

    __block NSString * localId;
    [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^
        PHAssetCollectionChangeRequest *assetCollectionChangeRequest = [PHAssetCollectionChangeRequest creationRequestForAssetCollectionWithTitle:@"XD"];
        localId = [[assetCollectionChangeRequest placeholderForCreatedAssetCollection] localIdentifier];
     completionHandler:^(BOOL success, NSError *error) 
        if (!success) 
            NSLog(@"Error creating album: %@", error);
         else 
            NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
            [prefs setObject:localId forKey:@"collection"];
            [prefs synchronize];
        
    ];

然后通过这个本地ID获取PHAssetCollection

NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
NSString* colletionId = [prefs stringForKey:@"collection"];
if(colletionId == nil) 
    colletionId = @"";


PHFetchResult *result = [PHAssetCollection fetchAssetCollectionsWithLocalIdentifiers:@[colletionId]  options:nil];
self.assetCollection = [result firstObject];

【讨论】：

谢谢！我能够根据我的需要调整您的样品。您是否有理由将 localId 存储到 *prefs 中而不是简单地使用 [result firstObject] 返回一个指针？

我存储它是因为我需要在其他地方使用它。可以直接使用指针。