Referencing a ViewController in AppDelegate - Objective C

Question

I am trying to get a NSMutableArray from another class. I am trying to reference that ViewController that contains the array. Lets say, a has the array I want. b is the class I am going to get that array in.

ah:

@property (strong, nonatomic) NSMutableArray *selectedCells;

am:

@synthesize selectedCells;

AppDelegate.h:

@property (strong, nonatomic) a *create_challengeDelegate;

AppDelegate.m:

@synthesize create_challengeDelegate;
a *create_challengeDelegate = [[a alloc]init];

Right here when I try to reference that ViewController I get an error saying:

Initializer element is not a compile-time constant

I assume it has something to do with it not being able to see the ViewController.

In my bm:

AppDelegate *app = (AppDelegate*)[[UIApplication sharedApplication] delegate];
app.create_challengeDelegate.selectedCells

My issue is working with initializing the ViewController in the delegate.

Suggestions and thoughts on that?

Answer 1

My suggestion is that you create the selectedCells array in you AppDelegate and send it to A . Eg in:

AppDelegate.h

@property (nonatomic, strong) NSArray *selectedCells;

AppDelegate.m

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.selectedCells = [NSMutableArray array];

    A *viewA = [[a alloc] initWithNibName:@"a" bundle:nil selectedCells:self.selectedCells];

    [...]
}

ah

@property (nonatomic, strong) NSMutableArray *selectedCells;

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil selectedCells:(NSMutableArray*)cells;

am

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil selectedCells:(NSMutableArray*)cells
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        self.selectedCells = cells;
    }
    return self;
}

bm

AppDelegate *app = (AppDelegate*)[[UIApplication sharedApplication] delegate];
NSMutableArray *selectedCells = app.selectedCells;

This way, whenever you make changes to selectedCells it will keep it in the array you send there since selectedCells is a refference to an object which is created in your AppDelegate .

Otherwise, what you are trying to do is access a view which might no longer be available in the memory since the view might have been deallocated. Also, you create the instance of a but its not set to the AppDelegate 's instance of a , its a seperate instance.

Instead of

@synthesize create_challengeDelegate;
a *create_challengeDelegate = [[a alloc]init];

You should have

@synthesize create_challengeDelegate;
self.create_challengeDelegate = [[a alloc] init];

I still strongly recommend you do not access your view this way though.

Ps @synthesize is no longer necessary.

Edit
This is a better solution.

Selection.h

/**
 *  The entity for selections
 */
@interface Selection : NSObject

/**
 *  The Shared Instance
 *
 *  @return Selection The instance
 */
+ (Selection *)sharedInstance;

/**
 *  Add an item to the selections
 *
 *  @param object id The object to add
 */
- (void)addSelection:(id)object;

/**
 *  Remove an item from the selections
 *
 *  @param object id The object to remove
 */
- (void)removeObject:(id)object;

/**
 *  Get the selections
 *
 *  @return NSArray The array with the current selection objects
 */
- (NSArray *)getSelections;

@end

Selection.m

#import "Selection.h"

@interface Selection ()

@property (nonatomic, strong) NSMutableArray *selections;

@end

@implementation Selection

#pragma mark - Public methods

+ (Selection *)sharedInstance
{
    static Selection *sharedInstance = nil;

    @synchronized(self) {
        if (sharedInstance == nil) {
            sharedInstance = [[self alloc] init];
        }
    }

    return sharedInstance;
}

#pragma mark - Private methods

- (id)init
{
    if (self = [super init])
    {
        self.selections = [NSMutableArray array];
    }
    return self;
}

#pragma mark - Manage selection

- (void)addSelection:(id)object
{
    [self.selections addObject:object];
}

- (void)removeObject:(id)object
{
    [self.selections removeOjbect:object];
}

- (NSArray *)getSelections
{
    return [NSArray arrayWithArray:self.selections];
}

Now you can assess your shared singeton in A and/or B by accessing:

[[Selection sharedInstance] addObject:myObject];

[[Selection sharedInstance] removeObject:myObject];

NSArray *array = [[Selection sharedInstance] getSelections];

Answer 2

Is this line inside a method:

a *create_challengeDelegate = [[a alloc]init];

If not that would probably explain your issue. If that's not the problem it might be helpful to post more complete code.