Question

I try adding objects to NSMutableArray from another class (secondViewController) and then add it to my UITableView in my FirstViewController, but it returns null when I print it using NSLog. Here is my set up.

FirstViewController.h:

@interface FirstViewController : UIViewController <UITableViewDelegate,UITableViewDataSource>{
    IBOutlet UITableView *mytableview;
    NSMutableArray *mytableinfo;
}
@property (nonatomic,retain) IBOutlet UITableView *mytableview;
@property (retain) IBOutlet NSMutableArray *mytableinfo;

FirstViewController.m

#import "FirstViewController.h"
#import "SecondViewController.h"
@synthesize mytableinfo,mytableview;
-(IBAction)addShift:(id)sender{
SecondViewController *secondViewController = [[SecondViewController alloc]init];
[self presentModalViewController:secondViewController animated:YES];
}
- (void)viewDidLoad
{
    mytableinfo = [[NSMutableArray alloc]init];
    [super viewDidLoad];
}

SecondViewController.m

#import "SecondViewController.h"
#import "FirstViewController.h"

@implementation SecondViewController
@synthesize dateformatter,mydatepicker,startingTime;

-(IBAction)saveShift:(id)sender{
    FirstViewController *firstViewController = [[FirstViewController alloc]init];
    [firstViewController.mytableinfo addObject:@"Hello world"];
    NSLog(@"%@",firstViewController.mytableinfo);
    [self dismissModalViewControllerAnimated:YES];
}

My goal is to ultimately feed a mytableviewfrom mytableinfo. I’m not even sure if this is the best way to go about it. Any advice would be appreciated.

Answer 1

In SecondViewController, you are creating a FirstViewController with alloc init. At that point, mytableinfo on FirstViewController is nil because you don’t allocate until viewDidLoad.

What loads SecondViewController? Because you’re dismissing it modally. If it’s FirstViewController, then when you alloc init first view controller, you’re not calling the instance that presented it modally.

It’s also not very MVC to have one view poke at another like that. It creates code that’s couple at the view layer and modifying data at the view layer. It is better to create a model and have both views modifying that model.

How to create a NSMutable Array which can access from different view controllers

Another way to communicate between views is for one view to pass a delegate (a callback) to the other view. That allows the other view to not be coupled to the other view – it only knows about the protocol for the delegate.

What exactly does delegate do in xcode ios project?