referencing an Mutable array from ClassA to Class B - objective-c

Question

could someone help me reference an array from a different class.
here is ClassA.h
#interface ClassA : UIViewController <MKMapViewDelegate> {
NSMutableArray *theArray;
}
#property (nonatomic, retain) NSMutableArray *theArray;
-(NSMutableArray *) pleaseReturnTheArray;
#end
ClassA.m
#import "ClassA.h"
#implementation ClassA
#synthesize theArray;
...
-(NSMutableArray *) pleaseReturnTheArray {
return theArray;
}
and here is ClassB.m (i want to reference ClassA array, i have #import "MapView.h" into this class, this is a different view that gets pushed onto the screen)
- (void)viewDidLoad {
[super viewDidLoad];
//first test
ClassA *firstTest = [[ClassA alloc] init];
NSMutableArray *firstTestArray = [firstTest.theArray mutableCopy];
NSLog(#"first test - %#", firstTestArray);
//second test
NSMutableArray *secondTestArray = [firstTest pleaseReturnTheArray];
NSLog(#"second Test - %#", secondTestArray);
...
the result in NSLog i get is ...
first test - (null)
second Test - (null)
I am sure i have used one of these methods before and it has worked fine. Is it something to do with the fact that ClassB is a different view pushed by a tab bar controller?
any help would be appreciated.
Chris

Answer 1

My initial guess here is that you are not initializing theArray to a real array in your init method of ClassA. By default it will be nil. So the mutableCopy will also be nil as is shown in your output. Or perhaps adding this line of code after allocating firstTest would help:
firstTest.theArray = [NSArray arrayWithObjects:#"A",#"B",nil];
Also the pleaseReturnTheArray method is redundant with the theArray getter. You might as well write the following line of code instead:
NSMutableArray *secondTestArray = firstTest.theArray;
Note that because you are taking a mutable copy for firstTestArray, firstTestArray and secondTestArray will be equal but they will not be the same arrays. That means that if you add something in firstTestArray it won't show up in secondTestArray and vice versa.