How can I access an NSMutableArray in a different class? - ios

Question

I declare the following in ViewController.h
#property (nonatomic, strong) NSMutableArray *locations;
and the following in ViewController.m
#implementation GHViewController
#synthesize locations;
...
for (FSFourSquareVenueObject *object in array) {
locations = [[NSMutableArray alloc] init];
[locations addObject:object.locationName];
NSLog(#"%#", locations);
}
This successfully logs all the string locations that have been placed in the locations NSMutableArray. How can I access this NSMutableArray in a different class?
I am trying to access it in my TableViewController class in order to display all the elements in the array. I have tried importing the ViewController.h file into my TableViewController.h file, yet I still cannot access the array from the ViewController class.

Answer 1

Remove the line
locations = [[NSMutableArray alloc] init];
from your for loop and place it somewhere like viewDidLoad or init. You're wiping out your array every time before adding a new object.
To access a single object across classes, you want to look into creating a singleton. There are many tutorials online.

Answer 2

Do as #Stonz2 suggests, but also modify your headers as follows:
In GHViewController.h:
#property (nonatomic, strong) NSArray *locations;
In GHViewController.m
#implementation GHViewController
#synthesize locations;
...
NSMutableArray *array = [[NSMutableArray alloc] init];
for (FSFourSquareVenueObject *object in array) {
[array addObject:object.locationName];
NSLog(#"%#", array);
}
self.locations = [array copy];
You can then access the array from another class using GHViewController -locations. You can edit the locations using the following snippet (or by creating a similar method in GHViewController):
NSMutableArray *array = [gh_viewController.locations mutableCopy];
[array addObject: newLocation];
gh_viewController.locations = [array copy];
Exposing a mutable array allows other class to modify the array without notifying GHViewController and vice versa. This can lead to unpredictable and hard to debug problems, such as if GHViewController removes some elements while TableViewController is iterating through all the objects. Using a non-mutable array prevents these sorts of bugs and ensures everyone has a consistent view of what's inside.