Messaging between two classes

I have a basic question about fetching values through different classes. I have a classA which fills an array (If i print it out it is not empty). LATER in class B i want to load this Array: I call a function from class A which returns the Array of class A. But in class B if i call my new array then is it null. I am a bit confused, because i think i retain every value of the array, but its still null. I tried also a lot of different possibilities. I think its a basic OOP syntax fault i produce?!

//CLASS_A.h

@interface classA {

       NSMutableArray* buoyArray;
 }

@property (nonatomic, retain) NSMutableArray * buoyArray;

-(NSMutableArray*)getArray:(NSMutableArray*)_array;

//CLASS_A.m

...        

-(NSMutableArray*)getArray:(NSMutableArray*)_array {
                _array=buoyArray;
                return _array;   
            }

//CLASS_B.h

#import "CLASS_A.h"


@class classA;
@interface classB ...

classA *mapSource;
NSMutableArray * buoyArray;
        }

@property(nonatomic开发者_如何学Python,retain) classA *mapSource;

//CLASS_B.m

buoyArray=[mapSource getArray:buoyArray];
NSLog(@"%@",buoyArray);

Actually you you are making new object of class A by calling alloc so by init it reintialize all properties values for that instance.

What you need,if you are pushing class B over class A then, fetch existing class A object from stack, by using this line.

mapSource = (ClassA *)[self.navigationController.viewControllers objectAtIndex: [self.navigationController.viewControllers count]-2];

then call this

buoyArray=[mapSource getArray:buoyArray];
NSLog(@"%@",buoyArray);