NSMutable阵列退出功能后不保留数据

Question

我有一个tableview，我试图用数据填充。我将值赋给函数中的数组。一切都保存起来，直到它离开searchWithLocation函数。看着日志，它让我觉得它与订购有关，就像我没有足够快地填充我的数据一样。或者这可能不是原因，我真的不知道。

- (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]; 
} 

日志：

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

你有异步执行程序的一种误解。每个完成处理程序可以在“调用”执行路径已经终止后执行。在你的情况下：

[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]); 

把代码移到里面的完成处理器后面。