Storing objects in an Array - iphone

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)
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Answer 1

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

Answer 2

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.

Answer 3

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

Answer 4

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