目标C中的SQLite3查询

Question

  -(IBAction)ButtonPressed:(id)sender
    { 
        const char *sql = "SELECT AccessCode FROM UserAccess";
        NSString *sqlns;
        sqlns = [NSString stringWithUTF8String:sql];
        if([Password.text isEqual:sqlns])
        {
            NSLog(@"Correct");
        }
            else {
                NSLog(@"Wrong");
            }

    NSLog(@"%@",sqlns);
    }

Noob here , At NSLog I am able to print "SELECT AccessCode FROM UserAccess" where as let say the access code is 1234 , which I want .The challenge is to execute the command so that I can retrieve 1234 from the Column AccessCode in the Table UserAccess in the datable UserAcess.sqlite My Database and table name are same oops . In the appdelegate I Have : ///

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    

    // Override point for customization after app launch 
    [self createEditableCopyOfDatabaseIfNeeded];    
    [window addSubview:viewController.view];
    [window makeKeyAndVisible];

    return YES;
}

///

 - (void)createEditableCopyOfDatabaseIfNeeded {

        NSLog(@"Creating editable copy of database");

        // First, test for existence.

        BOOL success;

        NSFileManager *fileManager = [NSFileManager defaultManager];

        NSError *error;

        NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

        NSString *documentsDirectory = [paths objectAtIndex:0];

        NSString *writableDBPath = [documentsDirectory stringByAppendingPathComponent:@"UserAccess.sqlite"];

        success = [fileManager fileExistsAtPath:writableDBPath];

        if (success) return;

        // The writable database does not exist, so copy the default to the appropriate location.

        NSString *defaultDBPath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"UserAccess.sqlite"];

        success = [fileManager copyItemAtPath:defaultDBPath toPath:writableDBPath error:&error];

        if (!success) {

            NSAssert1(0, @"Failed to create writable database file with message '%@'.", [error localizedDescription]);

        }

    }

///

+(sqlite3 *) getNewDBConnection{

    sqlite3 *newDBconnection;

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

    NSString *documentsDirectory = [paths objectAtIndex:0];

    NSString *path = [documentsDirectory stringByAppendingPathComponent:@"UserAccess.sqlite"];

    // Open the database. The database was prepared outside the application.

    if (sqlite3_open([path UTF8String], &newDBconnection) == SQLITE_OK) {

        NSLog(@"Database Successfully Opened :) ");

    } else {

        NSLog(@"Error in opening database :( ");

              }

              return newDBconnection;

              }

Please help :(

Answer 1

You need to make some sqlite3 calls to execute the select statement and retrieve the column values.

The sqlite3 quick start has everything in it you need to know for this particular task.