Beginning iOS 5 Application Development

CREATING AND OPENING A DATABASE

After the necessary library is added to the project, you can open a database for usage. You use the various C functions included with SQLite3 to create or open a database, as demonstrated in the following one-step Try It Out.

TRY IT OUT: Opening a Database

1. Using the Databases project created previously, define the openDB method in the DatabasesViewController.m file:

   -(void) openDB {
       //–-create database–-
       if (sqlite3_open([[self filePath] UTF8String], &db) != SQLITE_OK ) {
           sqlite3_close(db);
           NSAssert(0, @“Database failed to open.”);
       }
   }
   
   - (void)viewDidLoad
   {
       [self openDB];
       [super viewDidLoad];
   }

How It Works

The sqlite3_open() C function opens a SQLite database whose filename is specified as the first argument:

[self filePath] UTF8String]

In this case, the filename of the database is specified as a C string using the UTF8String method of the NSString class because the sqlite3_open() C function does not understand an NSString object.

The second argument contains a handle to the sqlite3 object, which in this case is db.

If the database is available, it is opened. If the specified database is not found, a new database is created. If the database is successfully opened, the function will return a value of 0 (represented using the SQLITE_0K constant).

The following list from www.sqlite.org/c3ref/c_abort.html shows the result codes returned by the various SQLite functions:

#define SQLITE_0K 0 /* Successful result */ #define SQLITE_ERR0R 1 /* SQL ...