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我有TabViewController2 个标签，第一个标签是我的Homescreen. 当我打开我的应用程序并且第一个选项卡显示它调用API.

API 调用

_loadingHistory = ([(AppDelegate *)[[UIApplication sharedApplication] delegate] updateInprogress]);
    if(([NetworkConnectivity hasConnection]) && ([(AppDelegate *)[[UIApplication sharedApplication] delegate] datasourceUpdateRequired]) && !([(AppDelegate *)[[UIApplication sharedApplication] delegate] updateInprogress]))
    {
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
            _loadingHistory = YES;
            [(AppDelegate *)[[UIApplication sharedApplication] delegate] setUpdateInprogress:YES];
            [self startOperationsForReferenceList];
            GetMostRecentEnquiryController *getRecent = [[GetMostRecentEnquiryController alloc] initWithPelicanId:[[NSUserDefaults standardUserDefaults] valueForKey:needId] NumberOfItems:100 Delegate:self];
            [getRecent fetchMostRecentData];

            if (!self.loadingHistory) {
                [self loadMostRecentHistory];
            }
        });
    } else {
        if (!self.loadingHistory) {
            [self loadMostRecentHistory];
        }
    }

我有一个MutableArray会收到API. 假设在API调用之后，它必须将一组值返回给我并放在MutableArray我创建的。在我的第一个标签中，它运行良好。第二个选项卡的作用与它所称的相同API。

但是，当我启动屏幕（显示第一个选项卡）时，立即单击第二个选项卡（当第一个选项卡正在加载时，这意味着API尚未完成），第二个选项卡将永远加载。但是当我再次单击第一个选项卡并返回到第二个选项卡时，详细信息就在那里。

获取最近的数据方法

if(![NetworkConnectivity hasConnection]) return;
ShowNetworkActivityIndicator();
NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"www.URI.com"];
ASIFormDataRequest *request = [ASIFormDataRequest requestWithURL:url];
[request setPostValue:[NSString stringWithFormat:@"%d",[self numberOfHistoryItems]] forKey:@"numbertofetch"];
[request setPostValue:[self neededId] forKey:@"neededId"];
[request setPostValue:@"commencement" forKey:@"sortby"];
[request setDelegate:self];
[request startSynchronous];
if(request.responseStatusCode == 200)
{
    [self.listOfAllItems removeAllObjects];
    [self.listOfFutureItems removeAllObjects];
    [self clearDatabase];
    NSData *jsonData = [request responseData];
    id result = [jsonData objectFromJSONData];
    HelloGetMostRecentEnquiries *userBase = [[HelloGetMostRecentEnquiries alloc] initWithDictionary:result];
    if([userBase isSuccess])
    {
        for (int i=0; i < userBase.enquiries.count; i++)
        {
            HelloEnquiries *enq = [[userBase enquiries] objectAtIndex:i];
            [self saveItemsToDatabase:enq];
        }
    }
    [(NSObject *)self.delegate performSelectorOnMainThread:@selector(finishedGetMostRecent:) withObject:self waitUntilDone:NO];
    HideNetworkActivityIndicator();
}
else
{
    HideNetworkActivityIndicator();
}
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