UITableView不会在HTTP请求后重新加载数据

Question

I'm trying to implement a search function in my application where after the user taps search on the keyboard an HTTP request will be sent to the API and the data returned will be displayed in my UITableView . However, it's not working and I think it because the request is running in a separate thread. I've tried a bunch of different solutions but none seem to work. Below is my code. Thanks for the help!

-(void)searchBarSearchButtonClicked:(UISearchBar *)searchBar{
    //get string from searchBar textfield
    NSString* searched = self.searchBar.text;

    //format the API call to search for the "searched" item (%@ after 'search/')
    NSString* formattedURL = [NSString stringWithFormat:@"https://api.nutritionix.com/v1_1/search/%@?results=0:100&fields=item_name,nf_total_fat,nf_protein,nf_total_carbohydrate&appId=f35a80a7&appKey=9263d4b1c216becb04681b1cd04d1815",searched];

    dispatch_async(dispatch_get_main_queue(), ^{
        [[[NSURLSession sharedSession] dataTaskWithURL:[NSURL URLWithString:formattedURL] completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {

            NSDictionary* foodsFoundDict = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableLeaves error:nil];

            //array holds an array of all the foods found from the API call
            NSArray* array;
            array = [foodsFoundDict valueForKey:@"hits"];

            //since the info needed is inside the dictionary @"fields" of each array element, loop through array and add each dictionary to the global searchedFoodsArray
            for(NSDictionary* dict in array){
                [self.searchedFoodsArray addObject:dict[@"fields"]];
            }
        }]resume];
        [self.tableView reloadData];

    });

}

Answer 1

Your problem appears to be that you're reloadData'ing the tableView outside of the completion block of the URL request. In addition, I'd take a second look at where you're putting tasks on the main queue.

Answer 2

I think the problem is you are wrapping main queue grabbing around the background process (NSURLSession call). NSURLSession is actually running in background. So you need to have the main queue GCD inside the NSURLSession block. For example:

    [[[NSURLSession sharedSession] dataTaskWithURL:[NSURL URLWithString:formattedURL] completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {

    // your code updating tableview datasource.

        dispatch_async(dispatch_get_main_queue(), ^{

                   [self.tableView reloadData];
        });

    }]resume];

Answer 3

Simply Add to your closure:

dispatch_async(dispatch_get_main_queue(), ^{

           [self.tableView reloadData];
});

If you want your search Results to update in a reactive manner. create a seperate array for Search Result and update your table view to use that array by checking self.searchBar.isActive