Question

I have an nsarray that when I NSLog it from one of my methods I can see its contents, but when I try to look inside it from elsewhere it seems to be empty. I am aware that my memory management needs some work, could anyone help explain whats happening here?

NEW CODE

WorkOutList.h

#import <UIKit/UIKit.h>


@interface WorkOutList : UIViewController {

    NSManagedObjectContext *managedObjectContext;
    NSMutableArray *customWorkouts;
    NSArray *passedWorkout;
}

@property(nonatomic, retain)NSManagedObjectContext *managedObjectContext;
@property(nonatomic, retain)NSMutableArray *customWorkouts;
@property(nonatomic, retain)NSArray *passedWorkout;

-(IBAction)customWorkouts:(id)sender;

-(void)passWorkoutBack:(NSArray *)workout;


@end

WorkOutList.m

@implementation WorkOutList

@synthesize managedObjectContext, customWorkouts, passedWorkout;

- (void)viewDidLoad {
    [self setupContext];
    NSLog(@"View Did Load");
    customWorkouts = [[NSMutableArray alloc] init];
    passedWorkout = [[NSArray alloc] init];
    [super viewDidLoad];
}

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];
    [self fetchWorkoutList];
    NSLog(@"View will Appear");
    NSLog(@"Array from View Will Appear : %@", passedWorkout);

}

-(IBAction)customWorkouts:(id)sender{
    CoCoachAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
    SelectedWorkout *selectedWorkout = [[SelectedWorkout alloc] initWithStyle:UITableViewStyleGrouped];

    [selectedWorkout recieveNeededData:customWorkouts];

    [appDelegate.practiceNavController pushViewController:selectedWorkout animated:YES];
    [selectedWorkout release];
}

-(void)passWorkoutBack:(NSArray *)workout{
    passedWorkout = workout;
    [passedWorkout retain];
}

- (void)dealloc {
    [super dealloc];
}

SelectedWorkout.h

#import <UIKit/UIKit.h>


@interface SelectedWorkout : UITableViewController {


    NSMutableArray *workoutListForTable;
}

@property(nonatomic,retain)NSMutableArray *workoutListForTable;

-(void)recieveNeededData:(NSMutableArray *)workoutList;

@end

SelectedWorkout.m(aside from all the stuff to set up the tableView)

    @implementation SelectedWorkout

    @synthesize workoutListForTable;

    -(void)recieveNeededData:(NSMutableArray *)workoutList{

        if (workoutListForTable != workoutList) {
            workoutListForTable = workoutList;  
        }

    - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
        [tableView deselectRowAtIndexPath:indexPath animated:YES];

        CoCoachAppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
        WorkOutList *workoutListView = [[WorkOutList alloc]init];

        [workoutListView passWorkoutBack:[workoutListForTable objectAtIndex:indexPath.row]];
        [appDelegate.practiceNavController popViewControllerAnimated:YES];
    }

    - (void)dealloc {

        [workoutListForTable release];
        [super dealloc];
    }


    NSLog(@"other table : %@", workoutListForTable);
    [workoutListForTable retain];
}

Answer 1

This is what I think I understand about the flow of your app:

1. passWorkoutBack gives your view controller an NSArray, which it places in ‘passedWorkout’.
2. viewDidLoad is called and your ‘passedWorkout’ is reinitialised as an empty array.
3. viewWillAppear is called and you realise your array is empty.

To be honest, I think this comes from a lack of understanding of designing robust code (don’t worry, it’s the hardest thing to learn in programming). Here are a few tips that I think would make this app flow smoother:

1. Create a new init method for your viewController class and, in it, include an argument to give pass this workout array.
2. If you get an array from somewhere, all you need to do is retain it (either by using a property as Inspire48 said, or by calling retain on the object as you’ve already done), you don’t even need to allocate or initialise the array before you get it from wherever you get it.
3. Understand the viewController lifecycle. Do you know the difference between viewDidLoad and viewWillAppear? If you don’t, learn, because they are both good tools when utilised properly.

Anywho, I hope this helped and that I wasn’t too ‘preachy’. I’m assuming a lot about your app and you, so correct me on anything I’m wrong about. Cheers.