Access NSMutableArray from other existing class - objective-c

Question

I'm trying to access a NSMutableArray from a different already existing class than it was created in. But if i NSLog it, i get null. My program starts up in class2, then I segue to class1, create my NSMutableArray by pressing one or more rows, and then I want my class2 to get the updated NSMutableArray instance, but all it get is null. Code below:
//class1.m
#import "FocusTagTableViewController.h"
#import "STATableViewController.h"
#implementation FocusTagTableViewController
#synthesize focusArray = _focusArray;
#synthesize allSelectedFocus = _allSelectedFocus;
- (void)viewDidLoad
{
_focusArray = [[NSArray alloc]initWithObjects:#"Balance",#"Bevægelse",#"Elementskift",#"Vejrtrækning",#"Alle",nil];
[super viewDidLoad];
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *selectedFocus = [[_focusArray objectAtIndex:indexPath.row] stringByAppendingString:#","];
if(_allSelectedFocus == nil)
{
_allSelectedFocus = [[NSMutableArray alloc]init];
[_allSelectedFocus addObject:selectedFocus];
}
else if(![_allSelectedFocus containsObject:selectedFocus])
{
[_allSelectedFocus addObject:selectedFocus];
}
}
//class2.m
#import "STATableViewController.h"
#import "FocusTagTableViewController.h"
#implementation STATableViewController
- (void)viewDidLoad
{
[super viewDidLoad];
FocusTagTableViewController *focusTag = [[FocusTagTableViewController alloc]init];
[focustag addObserver:self forKeyPath:#"allSelectedFocus" options:NSKeyValueObservingOptionNew context:NULL];
}
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
if([keyPath isEqualToString:#"allSelectedFocus"])
{
NSLog(#"%#", [object valueForKeyPath:keyPath]);
}
}

Answer 1

That's because in class 2 you create a new instance of class 1, wich has empty array.
If you want to access that array from class 2, you should make a reference to that first class. Or you could use Key-Value-Observing for that.
Here is the docs about KVO
http://developer.apple.com/library/mac/ipad/#documentation/Cocoa/Conceptual/KeyValueObserving/KeyValueObserving.html
In first class, when you create class two, add self as an observer for that array, and implement observeValueForKeyPath: method in class 1

Answer 2

Try this way:
1) Import your class2.h file in your class1 file.
2) Create an NSMutableArray *foo globally in your class2.h file
3) create an object for class2 in your class1 file
4) instead Of using allSelectedFocus in your class1 file, set objects to foo in that file itself like this [class2Object.foo addObject:selectedFocus];