Storing objects in an Array

Question

I'm working with a database, and trying to store the rows of a table as dictionary in an Array.

#import "RootViewController.h"
#import "ProgettoAppDelegate.h"
#import "AddItemViewController.h"
#import "DetailViewController.h"
#include <sqlite3.h>

@implementation RootViewController
@synthesize nibLoadedCell;
@synthesize addItem;

NSNumberFormatter *priceFormatter;
NSDateFormatter *dateFormatter;
NSMutableArray *shoppingListItems; <--i created here...
NSDictionary *editItem;

-(void) loadDataFromDb {
//apriamo il database
sqlite3 *db;
int dbrc; //Codice di ritorno del database (database return code)

ProgettoAppDelegate *appDelegate = (ProgettoAppDelegate *) [UIApplication sharedApplication].delegate;
const char *dbFilePathUTF8 = [appDelegate.dbFilePath UTF8String];
dbrc = sqlite3_open(dbFilePathUTF8, &db);
if (dbrc) {
    NSLog(@"Impossibile aprire il Database!");
    return;
}
//database aperto! Prendiamo i valori dal database.
sqlite3_stmt *dbps; //Istruzione di preparazione del database
NSString *queryStatementNS = @"select key, item, price, groupid, dateadded from shoppinglist order by item";
const char *queryStatement = [queryStatementNS UTF8String];
dbrc = sqlite3_prepare_v2(db, queryStatement, -1, &dbps, NULL);

//Richiamo la funzione sqlite3_step() finché ho righe nel database
while ((dbrc = sqlite3_step(dbps)) == SQLITE_ROW) {
    int primaryKeyValueI = sqlite3_column_int(dbps, 0);
    NSNumber *primaryKeyValue = [[NSNumber alloc] initWithInt:primaryKeyValueI];
    NSString *itemValue = [[NSString alloc] initWithUTF8String:(char*) sqlite3_column_text(dbps, 1)];
    double priceValueD = sqlite3_column_double(dbps, 2);
    NSNumber *priceValue = [[NSNumber alloc] initWithDouble:priceValueD];
    int groupValueI = sqlite3_column_int(dbps, 3);
    NSNumber *groupValue = [[NSNumber alloc] initWithInt:groupValueI];
    NSString *dateValueS = [[NSString alloc] initWithUTF8String:(char*) sqlite3_column_text(dbps, 4)];
    NSDate *dateValue = [dateFormatter dateFromString: dateValueS];

    NSMutableDictionary *rowDict = [[NSMutableDictionary alloc] initWithCapacity:5];
    [rowDict setObject:primaryKeyValue forKey: ID_KEY];
    [rowDict setObject:itemValue forKey: ITEM_KEY];
    [rowDict setObject:priceValue forKey: PRICE_KEY];
    [rowDict setObject:groupValue forKey: GROUP_ID_KEY];
    [rowDict setObject:dateValue forKey: DATE_ADDED_KEY];

    [shoppingListItems addObject: rowDict];
    NSLog(@"%d", [shoppingListItems count]); //I have a Breakpoint here!

    //rilascio tutti gli elementi
    [dateValue release];
    [primaryKeyValue release];
    [itemValue release];
    [priceValue release];
    [groupValue release];
    [rowDict release];
}
}

using Breakpoint at the end of the procedure, i can see that in the variables there are the contents of the database, but array "shoppingListItems" is empty. (count = 0)

If you are brave enough to take a look, here there is the entire project: http://cl.ly/9uvb

possible duplicate of [NSMutableArray addObject not affecting count?](http://stackoverflow.com/questions/3683761/nsmutablearray-addobject-not-affecting-count) and [NSMutableArray addObject: not working](http://stackoverflow.com/questions/1827058/nsmutablearray-addobject-not-working) — jscs, Sep 07 '11 at 02:32

score 1 · Answer 1 · answered Sep 07 '11 at 00:54

1

You have not shown the definition of shoppingListItems but there are two common problems when adding to an array:

The array is an NSArray and not a NSMutableArray as it must be
The array is nil - you may have created it using [NSMutableArray array] without explicit retain?

Yeah, checked your code - you never initialise it at all. Fix that and you should be OK.

answered Sep 07 '11 at 00:54

Adam Eberbach

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It's mutable, I created as `NSMutableArray *shoppingListItems;` – Oiproks Sep 07 '11 at 01:05
You defined it, but didn't create it. Until you assign something to that pointer (like shoppingListItems = [[NSMutableArray array] retain]) it is nil and addObject, as a message to nil, will do nothing. – Adam Eberbach Sep 07 '11 at 02:03

score 1 · Answer 2 · answered Sep 07 '11 at 00:56

1

I don't see anything in your code above that creates the array. If shoppingListItems is nil, then those -addObject: messages do nothing.

answered Sep 07 '11 at 00:56

NSResponder

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The array is a NSMutableArray created on top `#include @implementation RootViewController @synthesize nibLoadedCell; @synthesize addItem; NSNumberFormatter *priceFormatter; NSDateFormatter *dateFormatter; NSMutableArray *shoppingListItems;`... – Oiproks Sep 07 '11 at 01:01

D33pN16h7 · Accepted Answer · 2011-09-07T02:43:29.557

You need to declare all your variables as instance variables, i mean in the .h file as shown below

// .h
@interface RootViewController : UITableViewController {
    UITableViewCell *nibLoadedCell;
    AddItemViewController *addItem;
    IBOutlet UITableView *tableView;

    NSNumberFormatter *priceFormatter;
    NSDateFormatter *dateFormatter;
    NSMutableArray *shoppingListItems; // <--- this is only a declaration (not creates the object)
    NSDictionary *editItem;
}

And correctly initialize the objects, viewDidLoad is a good place to do this work:

//.m

- (void)viewDidLoad
{
    [super viewDidLoad];

    shoppingListItems = [NSMutableArray new]; // <---- This create the object
    // other initialization ....

    if (!dateFormatter) {
        dateFormatter = [[NSDateFormatter alloc] init];
        [dateFormatter setTimeZone: [NSTimeZone timeZoneWithAbbreviation:@"UTC"]];
        [dateFormatter setDateFormat:@"yyy-MM-dd HH:mm:ss"];
    }

    if (! priceFormatter) {
        priceFormatter = [[NSNumberFormatter alloc] init];
        [priceFormatter setNumberStyle:NSNumberFormatterCurrencyStyle];
    }
    self.navigationItem.leftBarButtonItem = self.editButtonItem;
}

Your problem resides on a nil value for shoppingListItems also dont forget to release the variable on your dealloc method

score 0 · Answer 4 · answered Sep 07 '11 at 00:52

0

It sounds like you aren't ever actually creating the array to go in shoppingListItems, so it's nil.

answered Sep 07 '11 at 00:52

Chuck

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I created! And i used this code in another project that do the same thing, but in the other one is working fine, here I have this strange problem... – Oiproks Sep 07 '11 at 01:06

Storing objects in an Array

4 Answers4