Objective-C: need to call a method in another class from FinishedLaunching - objective-c

Question

I got this far... here is my code:
- (void)applicationDidFinishLaunching:(UIApplication *)application
{
// create the d/b or get the connection value
SQLiteDB *dbInstance = [[SQLiteDB alloc] init];
}
Now, the question is: this bit of code is supposed to check to see if a database exists, and if not, create it. My problem is I am having a problem figuring out exactly how to write the first line of the called method and where to place it in SQLiteDB.m. Is this an instance method (-) or a class method (+)?
I'm sorry for being so lame on this, but once I see it, I'll have the hang of it... the rest of the code is written in C#, and I can handle the conversion to Obj_C.

Answer 1

The following is a method to copy an existing database from your Bundle to the Documents directory, but can easily be adapted for a new database. Just use the fileExistsAtPath: method logic below and replace the actions to take with your custom database creation code.
Put this in your AppDelegate.m file:
- (void)prepareDatabase
{
//add Database Versioning check to see if the resources database is newer
// generally as simple as naming your database with a version on the end
NSFileManager *filemanager = [NSFileManager defaultManager];
NSString *databasePath = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0] stringByAppendingString:#"/YOURDATABASE.s3db"];
if(![filemanager fileExistsAtPath:databasePath]) {
//Database doesn't exist yet, so we copy it from our resources
NSString *defaultDBPath = [[[NSBundle mainBundle] resourcePath] stringByAppendingString:#"/YOURDATABASE.s3db"];
if([filemanager copyItemAtPath:defaultDBPath toPath:databasePath error:nil]) {
NSLog(#"Database Copied from resources");
} else {
NSLog(#"Database copy FAILED from %# to %#",defaultDBPath,databasePath);
}
}
}
Then in your applicationDidFinishLaunching: method call this:
[self prepareDatabase];

Answer 2

I'm assuming that by "see if the database exists" you mean "see if the database file exists on disk". For that, you use method fileExistsAtPath: of class NSFileManager. It's an instance method, but you can use [NSFileManager defaultIntance].
Calculate the path to the file first (it's up to you how). Check if the file exists. If yes, open the file, if not, create a new database with that filename.