NSMutable配列は、終了後にデータを保持しません。

Question

データを取り込もうとしているtableViewがあります。関数内の配列に値を代入しています。 searchWithLocationの機能が終了するまで、すべてが保存されます。ログを見ると、データの順序が十分に速くならないように、注文と関係していると思います。それとも、それは理由ではない、私は本当に分かりません。

- (void)viewDidLoad { 
    [super viewDidLoad]; 

    venueName = [[NSMutableArray alloc] init]; 

    [YLPClient authorizeWithAppId:@"sdgsfgfgfg" 
          secret:@"aegsgdgdfs" 
       completionHandler:^ 
    (YLPClient *client, NSError *error) { 
     // Save your newly authorized client 
     self.client = client; 

     [self.client searchWithLocation:@"Chicago" 
         completionHandler:^ 
      (YLPSearch *search, NSError *error) { 
       for (YLPBusiness *business in search.businesses) { 
        [venueName addObject:business.name]; 
       } 
       NSLog(@"I return results: %lu", (unsigned long)[venueName count]); 
      }]; 
     NSLog(@"I return 0: %lu", (unsigned long)[venueName count]); 
    }]; 
} 

... 

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { 
    NSLog(@"number of rows in section: %lu", (unsigned long)[venueName count]); 
    return [venueName count]; 
} 

ログ：

2017-09-02 14:46:39.708 whatever[67890:8535793] number of rows in section: 0 
2017-09-02 14:46:39.714 whatever[67890:8535793] number of rows in section: 0 
2017-09-02 14:46:39.715 whatever[67890:8535793] number of rows in section: 0 
2017-09-02 14:46:40.448 whatever[67890:8535846] I return 0: 0 
2017-09-02 14:46:41.174 whatever[67890:8535846] I return results: 20 

Answer 1

あなたは、非同期プログラムの実行の誤解を持っています。完了ハンドラは、呼び出し元の実行パスが既に終了した後で実行できます。あなたの場合：

[self.client searchWithLocation:@"Chicago" 
       completionHandler: 
    // This completion handler can be executed after seconds, minutes or even hours. 
    ^(YLPSearch *search, NSError *error) 
    { 
    NSLog(@"As times go by – sometime in the future"); 
    for (YLPBusiness *business in search.businesses) 
    { 
     [venueName addObject:business.name]; 
    } 
    NSLog(@"I return results: %lu", (unsigned long)[venueName count]); 
    }]; 
    // This path is executed immediately. esp. likely before the cmpletion handler is executed 
    NSLog(@"It is now or never"); 
    NSLog(@"I return 0: %lu", (unsigned long)[venueName count]); 

コード内の完了ハンドラの後ろにコードを移動します。