Problem with adding data to a singleton mutablearray

DrJones · July 2011

Hi, i have a problem that i can't figure out. With some help from some nice guys in here i figured out how to use a singleton class. In the singleton class i have a mutablearray. The arra is shared to a class which have a tableview. There is a barbuttonitem which push you to a modal controller and when you hit save in that view a new object should be added to the array and tableview.

My class with the tableview looks like this:


- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    
    [DataContainerSingleto sharedDataContainerSingleto].arrayForSaved = [[NSMutableArray alloc] init];

}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    
    static NSString *MyIdentifier = @\"MyIdentifier\";
	
	UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:MyIdentifier];
	if (cell == nil) {
		cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:MyIdentifier] autorelease];
	}
	// Set up the cell
    
    cell.textLabel.text = [[DataContainerSingleto sharedDataContainerSingleto].arrayForSaved objectAtIndex:indexPath.row];
	
    return cell;
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    
    return [[DataContainerSingleto sharedDataContainerSingleto].arrayForSaved count];
}

i set my singleton array as the text in cellForRowAtIndex and make it count in numberOfRowsInSection. In the view did load method i alloc it.

In my modal controller the code looks like this when i hit the save button.


-(IBAction)save {
    
    [DataContainerSingleto sharedDataContainerSingleto].arrayForSaved = [[NSMutableArray alloc] init];
    
    [[DataContainerSingleto sharedDataContainerSingleto].arrayForSaved addObject:@\"Test\"];
    
    [self dismissModalViewControllerAnimated:YES];
}

Can someone help we figure out what is wrong please :)

- Jonas

Domele · July 2011

If you did that, you'd be overriding the array every single time you saved. Alloc the array in your singleton init method. Then just call addObject.

DrJones · July 2011

Domele;354722 said:
If you did that, you'd be overriding the array every single time you saved. Alloc the array in your singleton init method. Then just call addObject.

Okay, should i just call: -(id) init {

arrayForSaved = [[NSMutableArray alloc] init];
}

but then it says that its a non-void function. What should i do? i tried to return 0 but then it crashes when i run the save function :(

baja_yu · July 2011

Your method is missing the return value. Read up on initializing objects: Loading…

DrJones · July 2011

baja_yu;354866 said:
Your method is missing the return value. Read up on initializing objects: Loading…

Ahh, now my init method looks like this and when i push save in the modal controller it will just dismiss the modal view and show a empty tableview :(

-(id)init {

self =[super init];
If (self = super init) {
arraysForSaved = [[NSMutableArray alloc]init];
}
return self;
}

In my save function i do:

[[DataHandlerSingleto sharedDataHandlerSingleton].arrayForSaved addObject:@"Test"];

And then i dismiss the view. In my tableview class i make the singleton array count and cellForRow i use this to set the different rows:

cell.textLabel.text = [[DataHandlerSingleto sharedDataHandlerSingleton].arrayForSaved objectAtIndex:indexPath.row];

I can't figure out what im doing wrong :(

Domele · July 2011

What does the method sharedDataHandlerSingleton look like? Post the code.

DrJones · July 2011

Domele;354908 said:
What does the method sharedDataHandlerSingleton look like? Post the code.

In DataHandlerSingleto.h:

+(DataHandlerSingleto *)sharedDataHandlerSingleton;

Domele · July 2011

Post the code inside the method.

DrJones · July 2011

It doesnt have anything inside, maybe thats the problem. The reference i looked at just says that i need to have a global function.

Domele · July 2011

If you thought that calling an empty method would accomplish anything, you need to learn more about Objective C or programming in general.

Here is a tutorial on creating a Singleton: The Objective-C Singleton

DrJones · July 2011

Don't worry i know that compiling a empty method won't do anything, its because i downloaded a file, that did it for me so i should just call sharedMyClassName and then the file does it for me. But now i created my own singleton class, and it still won't work :(

SingletonData.h


#import <Foundation/Foundation.h>


@interface SingletonData : NSObject {
    
    NSMutableArray *arrayForSavedData;
}

@property (nonatomic, retain) NSMutableArray *arrayForSavedData;

+(SingletonData *)sharedDataInstance;

@end

SingletonData.m


#import \"SingletonData.h\"

@implementation SingletonData

@synthesize arrayForSavedData;

+(SingletonData *)sharedDataInstance {
    
    static SingletonData *sharedDataInstance;
    @synchronized(self) {
        
        if (!sharedDataInstance) {
            sharedDataInstance = [[SingletonData alloc] init];
        }
    }
    return sharedDataInstance;
}

-(id)init {
    
    self = [super init];
    if (!self) return nil;
    self.arrayForSavedData = [[NSMutableArray alloc] init];
    return self;
}

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

@end

Then i create a private in the delegate:

@private SingletonData *sharedData;

Launching with options i call:

sharedData = [SingletonData sharedDataInstance];

That should work fine. The annoying part comes when i create a object and put it into my array.

SavedCalculationsTableView.m


-(void)addSavedcalculation {
    
    AddInterface *add = [[AddInterface alloc] initWithNibName:@\"AddInterface\" bundle:nil];
    [self presentModalViewController:add animated:YES];
    [add release];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    
    static NSString *MyIdentifier = @\"MyIdentifier\";
	
	UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:MyIdentifier];
	if (cell == nil) {
		cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:MyIdentifier] autorelease];
	}
	// Set up the cell
    
    cell.textLabel.text = [sharedData.arrayForSavedData objectAtIndex:indexPath.row];
	
    return cell;
}

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    
    return [sharedData.arrayForSavedData count];
}

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

then it pushes the modal controller AddInterface.m


-(IBAction)save {
    
    [sharedData.arrayForSavedData addObject:@\"Test\"];

    [self dismissModalViewControllerAnimated:YES];
}

when i click save nothing happens its just a plain tableview, its like the cellForRow doesnt work together with a singleton array because if i create a normal array everything works fine. What should i do? :)

Domele · July 2011

First you are going to leak your property. It won't matter because it's a singleton but still. First, if you are going to alloc a property do it with this 3 step pattern:


NSMutableArray *mutableArray = [[NSMutableArray alloc] init];
self.arrayForSavedData = mutableArray;
[mutableArray release];

And then you have to release it in your dealloc method:


[arrayForSavedData]; //one way to do it
self.arrayForSavedData = nil //another way to do it

Try calling reloadData on your table view.

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