Empty UITableViewController with async calls - objective-c

Question

I am working on using NSURLSession and JSON serialization to fetch content from my site. The async calls and getting the JSON data work perfectly. My issue is, when it comes to displaying the data in the TableviewController, I put an NSLog statement to see if there is data and there is, but that cell.textlable.text never updates. I'm guessing the issue is the threads but I can't figure it out. Can you help?
#interface MainTableViewController :
UITableViewController<LokalModelProtocol>
#property (strong,nonatomic) NSMutableArray* arr;
#end
#implementation MainTableViewController
#synthesize arr;
- (void)viewDidLoad {
[super viewDidLoad];
arr = [[NSMutableArray alloc]init];
LokalModel *lokal = [[LokalModel alloc]init];
lokal.delegate=self;
[lokal downloadItems];
}
-(void)itemsDownloaded:(NSMutableArray *)items
{
arr=items;
//NSLog(#"%#", items);
[self.tableView reloadData];
}
#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
#warning Incomplete implementation, return the number of sections
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection: (NSInteger)section {
#warning Incomplete implementation, return the number of rows
// return 1;
return [arr count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:#"mainCell" forIndexPath:indexPath];
PostModel *post = [[PostModel alloc]init];
post =[arr objectAtIndex:indexPath.row];
NSLog(#"%#", post.postTitle); ////this outputs the correct strings///////
cell.textLabel.text =[NSString stringWithFormat:#"%#", post.postTitle];
cell.detailTextLabel.text = post.postTitle;///neither of these do//////
return cell;
}
#end
#protocol LokalModelProtocol <NSObject,NSURLSessionDelegate>
+(void)itemsDownloaded:(NSMutableArray*)items;
#end
#interface LokalModel : NSObject
-(void)downloadItems;
#property (strong, nonatomic) NSMutableData* thedata;
#property (strong, nonatomic) NSString* urlString;
#property (strong, nonatomic) NSURL* theUrl;
#property (strong,nonatomic) id<LokalModelProtocol>delegate;
+(void)parseJson:(NSData*)data;
#end
id<LokalModelProtocol>delegate;
#implementation LokalModel;
#synthesize thedata,urlString,theUrl,delegate;
-(void)downloadItems{
NSURL *theUrl = nil;
static NSString* urlString = #"https://balalatet.com/wp-json/wp/v2/posts";
theUrl=[NSURL URLWithString:urlString];
NSURLSession *currentSession= [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration]];
NSURLSessionDataTask *task = [currentSession dataTaskWithURL:theUrl completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
if (error){
[NSException raise:#"error" format:#"%#",error.localizedDescription];
NSLog(#"error1");
}
else{
NSLog(#"success");
[LokalModel parseJson:data];
}
}];
[task resume];
}
+(void)parseJson:(NSData*)data{
NSArray *jsonResults = [[NSArray alloc]init];
NSError *jsonerror;
jsonResults =[NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&jsonerror];
if (jsonerror)
[NSException raise:#"json error" format:#"%#",jsonerror.localizedDescription];
NSMutableArray *posts = [[NSMutableArray alloc] init];
NSMutableDictionary *jsonElenent =[NSMutableDictionary dictionary];
for (NSMutableDictionary *d in jsonResults)
{
jsonElenent=d;
PostModel *thePost=[[PostModel alloc]init];
thePost.postId= jsonElenent[#"id"];
thePost.postDate= jsonElenent[#"date"];
thePost.postDategmt= jsonElenent[#"date_gmt"];
thePost.postGuid= jsonElenent[#"guid"];
thePost.postSlug= jsonElenent[#"slug"];
thePost.postStatus= jsonElenent[#"status"];
thePost.postSticky= jsonElenent[#"sticky"];
thePost.postPingStatus= jsonElenent[#"ping_status"];
thePost.postType= jsonElenent[#"type"];
thePost.postCommentStatus= jsonElenent[#"comment_status"];
thePost.postTags= jsonElenent[#"tags"];
thePost.postTitle= jsonElenent[#"title"];
thePost.postTemplate= jsonElenent[#"template"];
thePost.postLink= jsonElenent[#"link"];
thePost.postMeta= jsonElenent[#"meta"];
thePost.postModified= jsonElenent[#"modified"];
thePost.postModifiedgmt= jsonElenent[#"modified_gmt"];
thePost.postFeaturedMedia= jsonElenent[#"featured_media"];
thePost.postFormat= jsonElenent[#"format"];
thePost.postLinks= jsonElenent[#"links"];
thePost.postAuthor= jsonElenent[#"author"];
thePost.postContent= jsonElenent[#"content"];
thePost.postCategory= jsonElenent[#"category"];
thePost.postExcerpt= jsonElenent[#"excerpt"];
NSLog(#"%#", thePost.postTitle);
[posts addObject:thePost];
}
dispatch_async(dispatch_get_main_queue(), ^{
[delegate itemsDownloaded:posts];
});
}
#end
Update
my apologies as part of my debugging info is incorrect. the nslog output did not come from the cellForRowAtIndexPath method. in fact the arr array remains empty because the
(void)itemsDownloaded:(NSMutableArray *)items
is never called. im sure i setup the protocol correctly. any thoughts on why the MainTableViewControllerClass cant get the data?
update
so i realized that i forgot to remove the line
id<LokalModelProtocol>delegate;
that i put right before the #implementation in LokalModel. but now doing so causes an error "unrecognized selector sent to instance" at the line
[delegate itemsDownloaded:posts];
I aslo tried
[self.delegate itemsDownloaded:posts];
but it throws the same exception.
Solved
My protocol method had to be an instance method, and i had it set as a class method.

Answer 1

Before return your cell add try to add this code in cellForRowIndexPath
[cell layoutIfneeded];

Answer 2

I believe you have to add a registerNib:forCellReuseIdentifier: or registerClass:forCellReuseIdentifier: prior to using dequeueReusableCellWithIdentifier:forIndexPath: (in viewDidLoad for example)
From the documentation: https://developer.apple.com/documentation/uikit/uitableview/1614878-dequeuereusablecellwithidentifie?language=objc
Important
You must register a class or nib file using the registerNib:forCellReuseIdentifier: or registerClass:forCellReuseIdentifier: method before calling this method.