找出当我的异步调用完成 [英] Find out when my asynchronous call is finished

问题描述

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。

<一个href=\"http://developer.apple.com/library/ios/#documentation/AssetsLibrary/Reference/ALAssetsLibrary_Class/Reference/Reference.html\">^[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]

这篇关于找出当我的异步调用完成的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！