Question

After trying out FMDB and SQLiteManager4iOS and failing miserably to access the table, I have decided not to use wrappers and so created an sqlite database AnimalDatabase.sql (in Terminal) with a table called ‘animals’ having two fields id, name.

The table currently looks like this.

+----------+
|1|Elephant|
|2|Giraffe |
+----------+

I want to display this data on the simulator, so I create a simple ViewController, with a button and a label. On clicking the button, either Elephant or Giraffe gets displayed on the label.

Interface – DatabaseTestViewController.h

#import <UIKit/UIKit.h>
#import <sqlite3.h>

@interface DatabaseTestViewController : UIViewController {
    IBOutlet UILabel* result;
    NSString *databasePath;
    NSMutableArray *animals;
}

@property(nonatomic,retain) NSString *databasePath;
@property(nonatomic,retain) NSMutableArray *animals;
@property(nonatomic,retain) IBOutlet UILabel *result;

-(IBAction) findResult;

@end

Implementation – DatabaseTestViewController.m

#import "DatabaseTestViewController.h"

@implementation DatabaseTestViewController
@synthesize databasePath,result,animals;

-(IBAction)findResult {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *docDir = [paths objectAtIndex:0];
    databasePath = [docDir stringByAppendingPathComponent:@"AnimalDatabase.sql"];
    NSFileManager *fileManager = [NSFileManager defaultManager];
    BOOL success = [fileManager fileExistsAtPath:databasePath];
    if(!success) {
        NSLog(@"File has to be copied");
        NSString *databasePathFromApp = [[[NSBundle mainBundle]resourcePath]stringByAppendingPathComponent:@"AnimalDatabase.sql"];
        [fileManager copyItemAtPath:databasePathFromApp toPath:databasePath error:nil];
        [fileManager release];
    }
    sqlite3 *database;
    animals = [[NSMutableArray alloc]init];
    if(sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK)
    {
        const char *sqlStatement = "select name from animals where id=2";
        sqlite3_stmt *compiledStatement;
        if(sqlite3_prepare_v2(database, sqlStatement, -1, &compiledStatement, NULL)==SQLITE_OK)
        {
            while(sqlite3_step(compiledStatement)==SQLITE_ROW)
            {
                NSLog(@"Name:%@",(char*)sqlite3_column_text(compiledStatement, 1));
                //[result setText:[NSString stringWithUTF8String:(char*)sqlite3_column_text(compiledStatement,1)]];
            }
        }
        sqlite3_finalize(compiledStatement);
    }
    sqlite3_close(database);
}

- (void)didReceiveMemoryWarning {[super didReceiveMemoryWarning];}
- (void)viewDidLoad {[super viewDidLoad];}
- (void)viewDidUnload {[super viewDidUnload];}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

@end

In the NSLog, I get

Name: (null) 

Please help me out by explaining what mistake I have made. Also, I am using Xcode 4.1.1 on Lion. I added the AnimalDatabase.sql next to .h and .m files on the project tree.

Answer 1

I’m unclear whether this is the only issue, but this is certainly a problem:

NSLog(@"Name:%@",(char*)sqlite3_column_text(compiledStatement, 1)); 

You get the value of the column, and tell the compiler that it’s a char* (i.e., a C data type). But then you tell Objective C that it’s an object (%@).

You can either convert the string into an NSString ([NSString stringWithCString:encoding:]) or tell NSLog that you’re using a null terminated string (%s).