Question

How would this work in this case? I created a NSMutabeArray *dataSource; in my .h file, but getting a bunch of errors:

“RootViewController.m: error: Semantic Issue: Property ‘dataSource’ not found on object of type ‘RootViewController *'”

RootViewController.h

#import <UIKit/UIKit.h>

@interface RootViewController : UITableViewController {
NSMutableArray *dataSource;
}

@property (nonatomic,retain) NSMutableArray *dataSource;
- (IBAction)addButton:(id)sender;

@end

RootViewController.m

#import "RootViewController.h"

@implementation RootViewController
@synthesize dataSource;

- (void)viewDidLoad
{
[super viewDidLoad];
self.dataSource = [NSMutableArray arrayWithCapacity:1];
//adds right bar button.
UIBarButtonItem *addButton = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(add:)];
self.navigationItem.rightBarButtonItem=addButton;
[addButton release];

}

-(void)addButton:(id)sender{
[self.dataSource addObject:@"New Item"];
NSIndexPath *newIndexPath = [NSIndexPath indexPathForRow:[self.dataSource count] inSection:0];
[self.dataSource insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
}

Answer 1

Some memory-guru will no doubt be able to tell you why @synthesize and mutable arrays and dictionaries (and sets, presumably) do not play well together. All I know is, initialize your mutable array explicitly and all will be well:

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.dataSource = [NSMutableArray arrayWithCapacity:1];

    //adds right bar button.
    UIBarButtonItem *addButton = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(add:)];
    self.navigationItem.rightBarButtonItem=addButton;
    [addButton release];
}

And, of course, release it in the dealloc.