How can I access an array from a different class and add more objects to it?

Question

MasterViewController.h:

#import <UIKit/UIKit.h>

@interface MasterViewController : UITableViewController

@property (nonatomic, strong) NSMutableArray *listOfBugs;

MasterViewController.m:

- (void)viewDidLoad
{
    [super viewDidLoad];
    _listOfBugs = [[NSMutableArray alloc]init];
}

...
...

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath

{
    ScaryBugDoc *bug = [self.bugs objectAtIndex:indexPath.row];
    [_listOfBugs addObject:bug];
}

In the above code I've created an array that holds objects with properties. I want to access the objects inside the array from a different class and also add objects to the same array. I know I can create a new array from the same class like this:

ListOfBugsViewController.m:

#import "ListOfBugsViewController.h"
#import "MasterViewController.h"
MasterViewController *myClass = [[MasterViewController alloc]init];


    NSMutableArray *array = [myClass.listOfBugs....

But obviously that's not what I'm looking for. I want to access the objects that are already inside the array and not to create a new array.

Edit: To make things a bit simpler, I have a few classes and only one array I'm adding objects to. All classes should be able to add objects to it and read previously added objects. How can I access that same array from a class it wasn't allocated and initialized in?

Thanks

Anoop Vaidya · Accepted Answer · 2012-12-06 12:07:48Z

1

Adding an object to an array from other class in fairly simple.

Just see how...

Base.m

...
_baseArray=[[NSMutableArray alloc]init];
[_baseArray addObject:@"Anoop"];
[_baseArray addObject:@"kumar"];
...

OtherClass.m

Base *baseObj=[Base new];
[baseObj.baseArray addObject:@"vaidya"];

EDIT:

As per our discussion

- (void)awakeFromNib
{
    [super awakeFromNib];
    [self createObjects];

}

- (void) createObjects
{
    _listOfBugs=[[NSMutableArray alloc]init];

    [_listOfBugs addObject:@"Anoop"];

    NSLog(@"init done, %@",_listOfBugs);

}


- (id)init
{
    self = [super init];    
    if (self) {
        [self createObjects];
    }
    return self;
}

edited Dec 6, 2012 at 12:07

answered Dec 6, 2012 at 8:29

Anoop Vaidya

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7 Comments

Segev Over a year ago

MasterViewController *baseObj=[MasterViewController new];      [baseObj.listOfBugs addObject:@"vaidya"];         [baseObj.listOfBugs addObject:@"test"];     NSLog(@"this is %@",([baseObj.listOfBugs objectAtIndex:0]));

I'm getting : ScaryBugs[2224:11303] this is (null) . Did I do something wrong?

Anoop Vaidya Over a year ago

in MasterViewController did you alloc+init listOfBugs in init method?

Anoop Vaidya Over a year ago

you are doing it in viewDidLoad, check by putting the above in init()

Segev Over a year ago

in MasterViewController I alloc+init listOfBugs inside viewDidLoad. Where is init() ?

Anoop Vaidya Over a year ago

create a method as : - (id)init { self = [super init]; if (self) { _baseArray=[[NSMutableArray alloc]init]; [_baseArray addObject:@"Anoop"]; [_baseArray addObject:@"kumar"]; } return self; }

|

James Webster · Accepted Answer · 2012-12-06 08:14:11Z

0

But obviously that's not what I'm looking for. I want to access the objects that are already inside the array and not to create a new array.

You're not creating a new array, you're creating a new pointer to an existing array. You can edit that array via this new pointer.

NSMutableArray *array = myClass.listOfBugs;
[array addObject:newBug];

However you don't have to create a new pointer, you can access the array directly via the property:

[myClass.listOfBugs addObject:newBug];

answered Dec 6, 2012 at 8:14

James Webster

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3 Comments

Segev Over a year ago

so [myClass.listOfBugs addObject:newBug]; is the only line I need to add to the new class without allocating and init it?

James Webster Over a year ago

Your question is a little confusing, but I think so yes.

Segev Over a year ago

I'll edit my first post now but adding just the above line of code gives me the error "Property 'listOfBugs' not found on object of type 'MasterViewController'"

sjs · Accepted Answer · 2012-12-06 08:25:24Z

0

Your question is confusingly worded. I think what you want is to access the listOfBugs property from a previously created instance of MasterViewController from your ListOfBugsViewController.

Is your ListOfBugsViewController being instantiated by your MasterViewController? If so you could add a new property to your ListOfBugsViewController to contain a pointer to the MasterViewController (make this property weak) and then have your MasterViewController set that pointer to itself right after it instantiates your ListOfBugsViewController.

answered Dec 6, 2012 at 8:25

sjs

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1 Comment

Segev Over a year ago

I've edited the first post. The code of the above can really help.

Zhang · Accepted Answer · 2012-12-06 08:38:30Z

The nice thing about Objective C is the objects are actually pointers to object instances. What's even nicer is when you pass an object, it's passed by reference (correct me if I am wrong).

You can simply call a method from your other class and pass in your source mutable array like so:

// ------------------------------------------
// Your "Other Class" .h header file
// ------------------------------------------

...

@interface OtherClass
{
    ...
}

...

+(void)addNewBugToArray:(NSMutableArray *)paramSourceArray;

@end

// ------------------------------------------
// Your "Other Class" .m implementation file
// ------------------------------------------

...

// ------------------------------------------
// Note: paramSourceArray is passed 
// by reference, meaning any change to it
// will affect the source array directly
// ------------------------------------------
+(void)addNewBugToArray:(NSMutableArray *)paramSourceArray
{
    [paramSourceArray addObject:@"newBug"];
}

...

@end




// ------------------------------------------
// Your Main View Controller .m file
// ------------------------------------------

#import "OtherClass.h"

...

-(void)viewDidLoad
{
   ...

   // initialize your source array
   sourceArray = [[NSMutableArray alloc] init];

   [btnAddBug addTarget:self selector:@selector(addNewBug) forControlEvent:UIControlEventTouchUpInside];

   ...

}

-(void)addNewBug
{
    // ---------------------------------------------------------
    // calling class method from "OtherClass" to add new bug
    // to our source array directly using pass by reference
    // ---------------------------------------------------------
    [OtherClass addNewBugToArray:sourceArray];
}

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