NSMutableArray as instance variable alway null

Question

After many hours wasted, I officially turn to the experts for help!

My problem lies with using a NSMutableArray as an instance variable, and trying to both add objects and return the array in a method in my class. I am obviously doing something fundamentally wrong and would be grateful for help...I have already tried all the suggestions from other similar questions on stackoverflow, read apples documentation, and basically all combinations of trial and error coding I can think of. The mutable array just alway returns (null). I've even tried creating properties for them, but still the array returns (null) and then I also am running into memory management problems due to the retain while setting the property, and the init in the init method for the class.

Here is what I am trying to do:

1) Loop through a series of UISwitches and if they are 'switched on', add a string to the NSMutableArray

2) Assign this mutable array to another array in another method

Any help much appreciated,

Andy

And for some code...

fruitsViewController.h

#import <UIKit/UIKit.h>

@interface fruitsViewController : UIViewController
{
    NSMutableArray *fruitsArr;
    UISwitch *appleSwitch;
    UISwitch *orangeSwitch;
}

@property (nonatomic,retain) NSMutableArray *fruitsArr; // ADDED ON EDIT
@property (nonatomic,retain) IBOutlet UISwitch *appleSwitch;
@property (nonatomic,retain) IBOutlet UISwitch *orangeSwitch;

- (IBAction)submitButtonPressed:(id)sender;
@end

fruitsViewController.m

#import "fruitsViewController.h"

@implementation fruitsViewController

@synthesize fruitsArr; // ADDED ON EDIT
@synthesize appleSwitch, orangeSwitch;

/* COMMENTED OUT ON EDIT
-(id)init
{
    if (self = [super init]) {
        // Allocate memory and initialize the fruits mutable array
        fruitsArr = [[NSMutableArray alloc] init];
    }
    return self;
}
*/

// VIEW DID LOAD ADDED ON EDIT
- (void)viewDidLoad
{
    self.fruitsArr = [[NSMutableArray alloc] init];
}

- (void)viewDidUnload
{
    self.fruitsArr = nil;
    self.appleSwitch = nil;
    self.orangeSwitch = nil;
}

- (void)dealloc
{
    [fruitsArr release];
    [appleSwitch release];
    [orangeSwitch release];
    [super dealloc];
}

- (IBAction)submitButtonPressed:(id)sender
{
    if ([self.appleSwitch isOn]) {
        [self.fruitsArr addObject:@"Apple"; // 'self.' ADDED ON EDIT
    }
    if ([self.orangeSwitch isOn]) {
        [self.fruitsArr addObject:@"Orange"; // 'self.' ADDED ON EDIT
    }
    NSLog(@"%@",self.fruitsArr); // Why is this returning (null) even if the switches are on?!
    [fruitsArr addObject:@"Hello World";
    NSLog(@"%@",self.fruitsArr); // Even trying to add an object outside the if statement returns (null)
}
@end

try to write alloc and init of array in viewDidLoad

KAREEM MAHAMMED
– KAREEM MAHAMMED

2012-02-03 10:27:30 +00:00
Commented Feb 3, 2012 at 10:27 — KAREEM MAHAMMED
– KAREEM MAHAMMED, Commented Feb 3, 2012 at 10:27

Simon Germain · Accepted Answer · 2012-02-03 10:26:29Z

7

It seems like your init function is never called. If you're initializing this view controller from a NIB, you need to use initWithCoder. If not, just declare your fruitsArr in viewDidLoad.

answered Feb 3, 2012 at 10:26

Simon Germain

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9 Comments

Simon Germain Over a year ago

Also, in viewDidUnload, self.fruitArr won't work. You didn't declare it as a property.

alex-i Over a year ago

it's initWithNibName:bundle: for UIViewControllers, not initWithCoder:.

Simon Germain Over a year ago

If the view controller was initialized through Interface Builder, it will use initWithCoder. If it's I initialized manually, then it's up to the person who creates it to call whatever function. The person isn't necessarily initializing it with a nib.

alex-i Over a year ago

sorry, I thought only the views have NSCoding protocol, not the viewcontrollers.

Simon Germain Over a year ago

No problem, just thought I'd clarify instead of being a giant butt. My last answer was a bit rude, sorry about that.

|

Inder Kumar Rathore · Accepted Answer · 2012-02-03 10:29:47Z

2

Use view did load instead of init...

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

answered Feb 3, 2012 at 10:29

Inder Kumar Rathore

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Comments

whtlnv · Accepted Answer · 2012-02-03 10:25:52Z

0

Change that init for viewDidLoad and see what happens

answered Feb 3, 2012 at 10:25

whtlnv

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Comments

alex-i · Accepted Answer · 2012-02-03 10:26:53Z

0

Is your init method ever being called (in complicationsViewController). Add a NSLog to check this, you might be calling initWithNib: maybe.

At viewDidUnload you should remove self.fruitsArr = nil;, or, if you want to keep it, then initialize the fruitsArr in viewDidLoad (and remove it from init).

answered Feb 3, 2012 at 10:26

alex-i

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Comments

Seamus · Accepted Answer · 2012-02-03 10:29:35Z

0

because fruitsArr don't be init. you should do this first: fruitsArr = [[NSMutableArray alloc] init];

so, I think you don't run - (id)init before you use fruitsArr.

answered Feb 3, 2012 at 10:29

Seamus

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