NSMutableArray is empty when reaches numberOfRowsInSection and cellForRowAtIndexPath - ios

Question

I am trying to to pretty standard operation, which is basically, getting all records form my local SQLITE database, then getting additional data form web, merge this data (which is NSMutableArray) and display it in table view. In viewDidLoad, array has all required elements, but in numberOfRowsInSection: it equals to nil. Because of this, I cannot display items in tableview. So where could it get set to nil? Thank you for any help.
Code for InboxViewControler.m
//
// ArticleViewController.m
// ReadLater
//
// Created by Ibragim Gapuraev on 09/06/2014.
// Copyright (c) 2014 Sermilion. All rights reserved.
//
#import "InboxViewController.h"
#import "LoginViewController.h"
#import "SHCTableViewCell.h"
#interface InboxViewController ()
#end
#implementation InboxViewController
#synthesize db, articles, response, jsonData;
- (NSMutableArray* ) articles
{
if (!articles) {
articles = [[NSMutableArray alloc] initWithCapacity:20];
}
return articles;
}
- (Database* ) db
{
if (!db) {
db = [[Database alloc] init];
}
return db;
}
//---------------------------------Getting data from web-------------------------------------------//
/**
The method will connect to a given url and send date of article that has been added at last.
Then, connectionDidFinishLoading will receive json array of all articles, that have been added to server database after that time
**/
#pragma mark Connection to server
- (void) makeConnetion:(id)data
{
NSMutableURLRequest * request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:#"http://localhost/nextril/index.php"] cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:15.0];
NSURLConnection * connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
//send id of article that was added last, to server,
//which will return json arrya of all articles with id greater then the one sent
[request setHTTPMethod:#"POST"];
[request setHTTPBody:[data dataUsingEncoding:NSUTF8StringEncoding]];
if (connection) {
NSLog(#"viewWillAppear: Connecting to server to get data...");
}else{
NSLog(#"viewWillAppear: Error while connecting...");
}
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData*)data
{
response = [[NSData alloc] initWithData:data];
}
//Check if data been received
- (void) connectionDidFinishLoading:(NSURLConnection *)connection
{
if(sizeof(response)>0){
//NSLog(#"Got response from server %#", response);
NSError* error;
NSArray* json = [NSJSONSerialization
JSONObjectWithData:response //1
options:kNilOptions
error:&error];
self.jsonData = [[NSMutableArray alloc] initWithArray:json];
int count = 0;
[self.db openDatabase];
BOOL added = false;
BOOL addedToUser = false;
NSLog(#"jsonData %d", jsonData.count);
for (int i=0; i<self.jsonData.count; i++) {
NSDictionary *item = [self.jsonData objectAtIndex:i];
NSString* content = [item objectForKey:#"content"];
NSString* author = [item objectForKey:#"author"];
NSString* date = [item objectForKey:#"date"];
NSString* url = [item objectForKey:#"url"];
NSString* tags = [item objectForKey:#"tags"];
NSInteger archived = [[item objectForKey:#"archived"]integerValue];
NSString* title = [item objectForKey:#"title"];
//NSLog(#"",);
Article* article = [[Article alloc]initWithId:0 content:content author:author date:date url:url tags:tags arhived:archived title:title];
added = [self.db addArticleToArticleDB:article];
if (added == true) {
NSInteger last_id = [self.db getLastArticleID];
article.article_id = last_id;
[self.articles addObject:article];
addedToUser = [self.db addArticleToUserArticleDB:article];
}
count++;
}
if (added == true && addedToUser == true) {
NSLog(#"connectionDidFinishLoading: Articles has been imported. Size: %d %lu", jsonData.count, (unsigned long)jsonData.count);
}else{
NSLog(#"connectionDidFinishLoading: Failed to import article.");
}
NSArray *importedArticles = [self.db importAllArticlesForUser:16 archived:0];
[self.articles addObjectsFromArray:importedArticles];
[self.db closeDatabase];
}else{
NSLog(#"connectionDidFinishLoading: Did not get resopnse from server: %#", response);
}
connection = nil;
}
//----------------------------------------------------------------------------------------------------
#pragma mark TODO: work out why data from server loads only after second login
#pragma mark view
- (void) viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
[self.db openDatabase];
NSString* date_added = [self.db getLastArticleDate];
[self makeConnetion:(id)date_added];
NSLog(#"viewWillAppear: self.articles: %d", self.articles.count);
[self.db closeDatabase];
}
- (void)viewDidLoad
{
[super viewDidLoad];
self.tableView.dataSource = self;
self.tableView.delegate = self;
self.tableView.separatorColor = [UIColor clearColor];
self.tableView.backgroundColor = [UIColor blackColor];
[self.tableView registerClass:[SHCTableViewCell class] forCellReuseIdentifier:#"Content"];
}
#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
// Return the number of sections.
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
// Return the number of rows in the section.
NSLog(#"numberOfRowsInSection: self.articles: %d", self.articles.count);
return self.articles.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Content";
SHCTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
cell.textLabel.backgroundColor = [UIColor clearColor];
NSMutableArray* safeArticles = self.articles;
// Configure the cell...
Article* article = [safeArticles objectAtIndex:indexPath.row];
NSString *listingKey = article.title;
NSString *listingValues = article.url;
cell.textLabel.text = listingKey;
cell.detailTextLabel.text = listingValues ;
cell.delegate = self;
cell.todoItem = article;
return cell;
}
#pragma mark cell atributes
-(UIColor*)colorForIndex:(NSInteger) index {
NSUInteger itemCount = self.articles.count - 1;
float val = ((float)index / (float)itemCount) * 0.6;
return [UIColor colorWithRed: 1.0 green:val blue: 0.0 alpha:1.0];
}
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
return 70.0f;
}
-(void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath {
cell.backgroundColor = [self colorForIndex:indexPath.row];
}
#pragma mark TODO delete from server database
//method to delete an article form view and to call method to delete from database, as well as form server database
-(void)deleteArticle:(Article*)articleToDelete {
. . .
}
#pragma mark TODO delete from server database
//method to delete an article form view and to call method to delete from database, as well as form server database
-(void)archiveArticle:(Article*)articleToArchive {
. . .
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#end

Answer 1

A tableView calls the datasource methods to populate itself just after viewDidLoad. If, at that point, the data source (which is usually an Array) is empty, nothing will appear in the tableView. That is why one has to call reloadData after the data source is brought into existence. This is especially needed in cases the data source is being fetched asyncronously.
According to Apple's documentation about reloadData:
Call this method to reload all the data that is used to construct the
table, including cells, section headers and footers, index arrays, and
so on. For efficiency, the table view redisplays only those rows that
are visible. It adjusts offsets if the table shrinks as a result of
the reload. The table view's delegate or data source calls this
method when it wants the table view to completely reload its data. It
should not be called in the methods that insert or delete rows,
especially within an animation block implemented with calls to
beginUpdates and endUpdates

Answer 2

Took advice of #akashg and added [self.tableView reloadData]; after fetching data. And it worked. Though, I don't know the mechanism of why this happened. At least it works ) Anyone welcome to add their explanation. Thank you.