retaining data outside of viewDidLoad in objective c ios

Question

I am aware this question has been asked previously, but the answers provided have not solved my issue.

For instance, I have a very simple array of objects outlined in viewDidLoad:

@implementation MyViewController {
NSArray *tableData;
}

---

- (void)viewDidLoad
{
   [super viewDidLoad];
   tableData = [NSArray arrayWithObjects:@"Hello", @"My", @"Name", @"Is"];
   NSLog(@"My Data: %@", tableData);

which is called in a tableView using cellForRowAtIndexPath

cell.nameLabel.text = [tableData objectAtIndex:indexPath.row];

This works fine and the NSLog shows my array. However, when i outline tableData outside of viewDidLoad, my array is (null).

My question is, how do I make my array available for the tableView when it is specified outside of ViewDidLoad?

edit: Here is my specific code:

#import <UIKit/UIKit.h>
#import "PhotoView.h"
@interface FrontViewController : UIViewController

@property (nonatomic, retain) UITableView *tableView;

@end

---

#import "FrontViewController.h"
#import "StreamScreen.h"
#import "API.h"
#import "PhotoView.h"
#import "StreamPhotoScreen.h"
#import "PrivateViewController.h"
#import "SWRevealViewController.h"
#import "PhotoScreen.h"
#import "RearViewController.h"
#import "SimpleTableCell.h"



@interface FrontViewController()

// Private Methods:
- (IBAction)pushExample:(id)sender;

@end

@implementation FrontViewController{
    NSArray *tableData;

}

#pragma mark - View lifecycle


- (void)viewDidLoad
{
    [super viewDidLoad];

    self.title = NSLocalizedString(@"Front View", nil);

    SWRevealViewController *revealController = [self revealViewController];

    [self.navigationController.navigationBar addGestureRecognizer:revealController.panGestureRecognizer];

    UIBarButtonItem *revealButtonItem = [[UIBarButtonItem alloc] initWithImage:[UIImage imageNamed:@"reveal-icon.png"]
                                                                     style:UIBarButtonItemStyleBordered target:revealController action:@selector(revealToggle:)];

    self.navigationItem.leftBarButtonItem = revealButtonItem;

    // This works if I uncomment
    //tableData = [NSArray arrayWithObjects:@"Hello", @"My", @"Name", @"Is", nil];

    [self refreshStream];

}




-(void)refreshStream {
    // call the "stream" command from the web API
    [[API sharedInstance] commandWithParams:
     [NSMutableDictionary dictionaryWithObjectsAndKeys:@"stream", @"command", nil]
                           onCompletion:^(NSDictionary *json) {
                               //got stream

                               [self showStream:[json objectForKey:@"result"]];
                               NSMutableArray *myData = [[NSMutableArray alloc] init];
                               myData = [json objectForKey:@"result"];
                               NSArray *userNameData = [myData valueForKey:@"username"];


                               [self loadData];

                               tableData = userNameData;


                               [self.tableView reloadData];
                               // I can see my json array in NSLog
                               NSLog(@"here's the results: %@", tableData);
                           }];

}
//This doesn't work either
//-(void)loadData {

    // Add the data to your array.
    //tableData = [NSArray arrayWithObjects:@"Hello", @"My", @"Name", @"Is", nil];
    //NSLog(@"My Data: %@", tableData);

   // Now load the table view.
  //  [self.tableView reloadData];
//}


-(void)showStream:(NSArray*)stream {

    for (int i=0;i<[stream count];i++) {
        NSDictionary* photo = [stream objectAtIndex:i];


    }
    NSArray *checkData = [stream valueForKey:@"username"];
    //I can see my data in NSLog
    NSLog(@"here's the results: %@", checkData);
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return [tableData count];
}

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    return 78;
}


- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *simpleTableIdentifier = @"SimpleTableCell";

    SimpleTableCell *cell = (SimpleTableCell *)[tableView dequeueReusableCellWithIdentifier:simpleTableIdentifier];
    if (cell == nil)
    {
        NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"SimpleTableCell" owner:self options:nil];
        cell = [nib objectAtIndex:0];
}

    cell.nameLabel.text = [tableData objectAtIndex:indexPath.row];
    cell.thumbnailImageView.image = [UIImage imageNamed:[thumbnails objectAtIndex:indexPath.row]];
    cell.prepTimeLabel.text = [prepTime objectAtIndex:indexPath.row];

    return cell;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSLog(@"didSelectRowAtIndexPath");
    /*UIAlertView *messageAlert = [[UIAlertView alloc]
 initWithTitle:@"Row Selected" message:@"You've selected a row" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];*/
UIAlertView *messageAlert = [[UIAlertView alloc]
                             initWithTitle:@"Row Selected" message:[tableData objectAtIndex:indexPath.row] delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];

    // Display the Hello World Message
    [messageAlert show];

    // Checked the selected row
    UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath];
    cell.accessoryType = UITableViewCellAccessoryCheckmark;

    [tableView deselectRowAtIndexPath:indexPath animated:YES];
}

- (NSIndexPath *)tableView:(UITableView *)tableView willSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSLog(@"willSelectRowAtIndexPath");
    if (indexPath.row == 0) {
        return nil;
     }

   return indexPath;
}
@end

Answer 1

-(void)refreshStream {
    // call the "stream" command from the web API
    [[API sharedInstance] commandWithParams:
        [NSMutableDictionary dictionaryWithObjectsAndKeys:@"stream", @"command", nil] 
        onCompletion:^(NSDictionary *json) {
            //got stream

            [self showStream:[json objectForKey:@"result"]];
            NSMutableArray *myData = [json objectForKey:@"result"];
            NSArray *userNameData = [myData valueForKey:@"username"];
    }];

    tableData = userNameData;

    [self.tableView reloadData]; 
}

You're falling into a very common trap with asynchronous programming here.

commandWithParams takes a completion block, which is where you are getting the data out of the JSON. This block is not executed until the API call has returned. The sequence of events that happens when you run this code is:

1. commandWithParams is called
2. tableData is assigned to the contents of userNameData (which presumably you've also declared somewhere else otherwise this would not even compile)
3. reloadData is called
4. .... time passes
5. The completion block is executed and the JSON is read out into local variables, which are then instantly destroyed.

You need to move the two lines (points 2 and 3 in the list above) inside the completion block. There will be no data for your table until the block returns.

Answer 2

Ok my understanding of your question is that you want to assign variables to your NSArray in another method (not viewDidLoad) and then load the table view.

This is simple, just make a method which is in charge of adding the data to your array and then reload your table view like so:

-(void)viewDidLoad {
    [super viewDidLoad];

    // Call your method.
    [self loadData];
}

-(void)loadData {

    // Add the data to your array.
    tableData = [NSArray arrayWithObjects:@"Hello", @"My", @"Name", @"Is"];
    NSLog(@"My Data: %@", tableData);

    // Now load the table view.
    [myTableView reloadData];
}

Update 1

It would be much more helpful if you could share your code with us. How your and setting up your tableview, when its being called/etc....

Update 2

Ok well it seems obvious what yoru issue is. Your table view will never load like that. You need to call the tableview reloadData method outside the cellForRowAtIndexPath method.

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{

    static NSString *simpleTableIdentifier = @"SimpleTableCell";

    SimpleTableCell *cell = (SimpleTableCell *)[self.tableView dequeueReusableCellWithIdentifier:simpleTableIdentifier];

    if (cell == nil) {
        NSArray *nib = [[NSBundle mainBundle] loadNibNamed:@"SimpleTableCell" owner:self options:nil];
        cell = [nib objectAtIndex:0];
    }

    cell.nameLabel.text = [tableData objectAtIndex:indexPath.row];
    cell.thumbnailImageView.image = [UIImage imageNamed:[thumbnails objectAtIndex:indexPath.row]];
    cell.prepTimeLabel.text = [prepTime objectAtIndex:indexPath.row];

    return cell;   
}

So the method call [self.tableView reloadData]; should only be called in your refreshStream method.

Update 3

You need to initialize your NSMutableArray before you can add data to it. initialize it in your refreshStrem method like so:

-(void)refreshStream {

    // call the "stream" command from the web API
    [[API sharedInstance] commandWithParams:[NSMutableDictionary dictionaryWithObjectsAndKeys:@"stream", @"command", nil] onCompletion:^(NSDictionary *json) {
    //got stream

        [self showStream:[json objectForKey:@"result"]];

        NSMutableArray *myData = [[NSMutableArray alloc] init];
        myData = [json objectForKey:@"result"];

        NSArray *userNameData = [myData valueForKey:@"username"];
    }];

    tableData = userNameData;
    [self.tableView reloadData];
}

Update 4

Ok well after reading @jrturton answer, I think its safe to assume that my answer is rubbish. To anyone reading my answer, please view @jrturton post.

Answer 3

Well I feel pretty sheepish. The answer was simple. I was so hung up on Json and API that all I didn't check the basics. All I need was in my .h file:

@property (strong, nonatomic) IBOutlet UITableView *tableView;

I had originally had:

@property (nonatomic, retain) UITableView *tableView;