找出当我的异步调用完成

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我通过相册的iOS设备上的列表进行迭代。通过这组已经反复之后，我想简单地打印出被发现专辑的数量。

我有什么在我的code改变了的NSLog 语句只执行，当所有的专辑被加载。

ALAssetsLibrary *库= [[ALAssetsLibrary的alloc]初始化];NSMutableArray里* tempArray = [[NSMutableArray里的alloc]初始化];无效（^ groupBlock）（ALAssetsGroup *，* BOOL）= ^（ALAssetsGroup *组，BOOL *停止）{    如果（集团==无）{回报;}    [tempArray ADDOBJECT：组]; };无效（^ failureBlock）（NSError *）= ^（NSError *错误）{    的NSLog（@时发生问题％@，[错误描述]）;};[库enumerateGroupsWithTypes：ALAssetsGroupAll                       usingBlock：groupBlock                     failureBlock：failureBlock];的NSLog（@％我的专辑被装，tempArray.count）;

解决方案

您 groupBlock 将获得一组无当枚举完成的，所以改变：

如果（集团==无）{回报;}

到

的NSLog（@％我的专辑被装，tempArray.count）;

从类引用：

  

在枚举完成后，的 enumerationBlock 的调用与设置为无组。

[source]

I iterate through a list of photo albums on a iOS device. After having iterated through this group I want to simply print out the number of albums that were found.

What do I have to change in my code that the NSLog statement is only executed, when all the albums were loaded.

ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init]; NSMutableArray *tempArray = [[NSMutableArray alloc] init]; void (^groupBlock)(ALAssetsGroup *, BOOL *) = ^(ALAssetsGroup *group, BOOL *stop){ if (group == nil){return;} [tempArray addObject:group]; }; void (^failureBlock)(NSError *) = ^(NSError *error) { NSLog(@"A problem occured %@", [error description]); }; [library enumerateGroupsWithTypes:ALAssetsGroupAll usingBlock:groupBlock failureBlock:failureBlock]; NSLog(@"%i albums were loaded", tempArray.count);

解决方案

Your groupBlock will receive a group of nil when the enumeration is completed, so change:

if (group == nil){return;}

to

NSLog(@"%i albums were loaded", tempArray.count);

From the Class reference:

When the enumeration is done, enumerationBlock is invoked with group set to nil.

[source]