I am trying to find some source code on how to access and store variables from a database to my program via obj-c(iPhone). I have look for many hours now and no one has provided a sure fire way on how to go about this. If you have any advice or recommendations please post some source code or a link to it.
Thanks for the help.
If using the sqlite3 database which your program has access to on the phone for local database storage.
#import <sqlite3.h>
And create an openDatabase() method. Also add a variable for keeping the db around.
sqlite3 *db = nil;
Just make sure you call your open database method before using the database. Check this page out http://ved-dimensions.blogspot.com/2009/03/iphone-development-sqlite3-populating.html
Might give you something that you can use.
+(sqlite3 *) getNewDBConnection{
sqlite3 *newDBconnection;
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *path = [documentsDirectory stringByAppendingPathComponent:#"data.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;
}
Related
I have an sql file in my supporting files. How can I open this file so that I can start using SQL commands to get the information that I want? I've tried a couple different syntaxes, and the last time I tried I ended up screwing up the whole application because I couldn't remember what I had changed.
If you are using sqlite 3. Then,
NSArray* paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString* documentsDirectory = [paths lastObject];
NSString* dbPath = [documentsDirectory stringByAppendingPathComponent:#"database.sqlite"];
if(sqlite3_open([dbPath UTF8String], &dataBase) == SQLITE_OK)
{
NSLog(#"Opened Database");
//Your code
}
else
{
NSLog(#"Failed to open database");
sqlite3_close (database);
}
I have an iPhone app that use an Sqlite database to store some data and some user configurations. The problem that I'm having is that when I submit an update of my application, the existing database on the user installation is overwrite with the empty database and the users lost their configurations. I'm sure it can not be too difficult to avoid this, but I don't know how to do it.
This is my code of the method that create the copy of the db:
// Creates a writable copy of the bundled default database in the application Documents directory.
- (void)createEditableCopyOfDatabaseIfNeeded {
// First, test for existence.
BOOL success;
NSFileManager *fileManager = [NSFileManager defaultManager];
NSError *error;
NSString *writableDBPath = [self databasePath];
success = [fileManager fileExistsAtPath:writableDBPath];
if (!success) {
// The writable database does not exist, so copy the default to the appropriate location.
//NSLog(dbName);
NSString *defaultDBPath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:dbName];
success = [fileManager copyItemAtPath:defaultDBPath toPath:writableDBPath error:&error];
if (!success) {
NSAssert1(0, #"Failed to create writable database file with message '%#'.", [error localizedDescription]);
}
}
}
This method is called form:
- (BOOL)openDatabase {
BOOL success = true;
if (!database) {
[self createEditableCopyOfDatabaseIfNeeded];
if (sqlite3_open([[self databasePath] UTF8String], &database) != SQLITE_OK) {
success = false;
// Even though the open failed, call close to properly clean up resources.
sqlite3_close(database);
NSAssert1(0, #"Failed to open database with message '%s'.", sqlite3_errmsg(database));
}
}
return success;
}
- (NSString*)databasePath {
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *path = [documentsDirectory stringByAppendingPathComponent:dbName];
return path;
}
Maybe I forgot something in my code?
Can some one help me to solve this out? Thank you!
How about copying the sqlite database from your main bundle to the application's document directory, but only if it does not already exist?
If you are using Core Data, or using sqlite - you are probibly storing your data in the "Documents" directory. This will not be wiped-out when updating your app.
I don't know much about sqlite databases, except that they are in-memory databases. It is not possible to 'keep' the in-memory databases. You have two options:
1) find a way to configure your sqlite to use a file instead of running in-memory (I don't know if this is possible, I looked but couldn't find a way quickly)
2) switch to a different database provider. If the pc is yours, you can install xampp or wamp (lamp on linux), containing a pre-configured, ready-to-run MySql database.
A final way would be to temporarily store the sqlite data when exiting and then reload it on startup, but that doesn't seem very optimal!
If you don't really need a database, you could also consider alternate storing such as xml or a flatfile
I've got the following iphone code, which seems to be failing:
sqlite3_stmt *dbps;
NSString *sql = #"delete from days where day=?1;insert into days(disabled,recipe_id,day) values(?2,?3,?1)";
int rc = sqlite3_prepare_v2(db, sql.UTF8String, -1, &dbps, NULL);
...
The 'rc' return code is 1, meaning SQLITE_ERROR (SQL error or missing database, according to the sqlite site). Not sure what i've done wrong? The database 'db' is indeed open, and other queries seem to work fine.
Thanks a lot guys
Remove the insert statement from your string. It is not compiled anyway since sqlite3_prepare_v2 will "only compile the first statement in zSql."
Perhaps you should use a trigger to do your (optional) delete, or use insert or replace.
Are you sure you have copied the database in Documents directory before opening it? iPhone OS only allow write permissions in documents directory. Here is the code for copying database to Documents directory -
//function to copy database in Documents dir.
-(void) checkAndCreateDatabase{
// Check if the SQL database has already been saved to the users phone, if not then copy it over
BOOL success;
// Create a FileManager object, we will use this to check the status
// of the database and to copy it over if required
NSFileManager *fileManager = [NSFileManager defaultManager];
// Check if the database has already been created in the users filesystem
success = [fileManager fileExistsAtPath:databasePath];
// If the database already exists then return without doing anything
if(success) return;
// If not then proceed to copy the database from the application to the users filesystem
// Get the path to the database in the application package
NSString *databasePathFromApp = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:databaseName];
// Copy the database from the package to the users filesystem
[fileManager copyItemAtPath:databasePathFromApp toPath:databasePath error:nil];
[fileManager release];
}
// open the database and fire the delete query...
sqlite3 *database;
NSString *sqlStatement = #"";
NSArray *documentPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDir = [documentPaths objectAtIndex:0];
databasePath = [documentsDir stringByAppendingPathComponent:databaseName];
NSLog(#"%#",databasePath);
[serlf checkAndCreateDatabase];
if(sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK)
{
// here you can fire the delete query...
}
Silly me, i just had an old copy of the schema in my Documents folder, which didn't have the 'days' table in it. So i followed the instructions here: Cleaning up the iPhone simulator, and then it copied the new schema over, and it started working again.
Thanks for the help guys.
I am programming an Xcode iPhone app and utilizing sqlite. In an effort to delete all rows from a table, I receive the warning above when I build my code. Does anyone have any suggestions on how to fix this?
Thanks
- (void) deleteData {
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *writableDBPath = [documentsDirectory
stringByAppendingPathComponent:#"myDatabase.sqlite"];
if (sqlite3_open([writableDBPath UTF8String], &database) == SQLITE_OK) {
[database executeNonQuery:#"DELETE FROM test;"];
}
[database release];
}
Assuming
sqlite3 *database;
somewhere all up ins, it should be noted that sqlite3_open() doesn't create an Objective-C object; it creates an sqlite3 database handle, which is, if memory serves, a struct packed in a pointer. It can, in other words, not receive Objective-C messages. * does not an object make.
I'm trying to build a class for handling all sqlite3 work and I've encountered an EXC_BAD_ACCESS which I just can't explain. I am new to Objective-C development and memory management in general so I apologize if this is a stupid question.
When initializing the class I get the path to the database file and keep it around:
NSArray * documentPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
databasePath = [[[documentPaths objectAtIndex:0] stringByAppendingPathComponent:#"Database.sql"] retain];
Then I try to use it and it crashes on me:
if (sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK) { // crashes
The odd thing is that the exact same line in a different function works perfectly. I tried adding the variable initialization to above the line, but to no avail:
NSArray * documentPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
databasePath = [[[documentPaths objectAtIndex:0] stringByAppendingPathComponent:#"Database.sql"] retain];
if (sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK) { // crashes
In both cases the retain count is 2.
However, putting any form of static text in there works fine:
databasePath = #"I have a balloon";
if (sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK) { // fine
// or
if (sqlite3_open([#"APPLES!" UTF8String], &database) == SQLITE_OK) { // fine
A little more experimentation revealed that it was the UTF8String function that was crashing, but I don't understand why.
Edit: Even more experimentation resulted in me being able to call the UTF8String function but not even use the results:
const char * test = [databasePath UTF8String];
NSLog(#"%#", [NSString stringWithUTF8String:test]); // fine
if (sqlite3_open(test, &database) == SQLITE_OK) { // fails
Edit: Messed around even more and discovered that the problem was in a parameter that I was passing to the function. I had breakpoints all over the place so I was 100% sure that the point it fails is at the line I specified, a line which doesn't use the passed variable, but somehow it caused everything to fail. Sometimes. I have no idea how it went wrong, but I rewrote the entire thing, changed my function call and now it works.
Thanks to all who answered.
Have you checked the contents of the databasePath variable before the open call is made? Add an NSLog statement, or use the debugger, to find its value – it could be either NULL, which may not be handled by the sqlite3_open function, or it could even be that the crash is because the path is valid, and the database it points to is corrupt.
My guess is that the database variable is not declared properly. It doesn't seem to have anything to do with the path to the database.
Did you declare database like this?:
sqlite3 *database;
I suspect you are chasing the wrong problem. You haven't shown a crash dump but claim that opening "APPLES!" is 'fine' which sounds odd - surely you don't have a database with that name?
Are you sure you don't have a bad database file lying around - ie, the database file you are trying to open is corrupted in some way?
I think you have to post the crash log, your crash makes no sense. The code you posted should work.
Try a copy instead of a retain on the variable - it'll make an immutable copy of the string so it shouldn't go changing or disappearing.
EDIT::
What happens when you simply type
if (sqlite3_open[#"myDatabase.sqlite" UTF8String], &database) == SQLITE_OK) {
Also are you sure that the
NSArray * documentPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
databasePath = [[[documentPaths objectAtIndex:0]
stringByAppendingPathComponent:#"Database.sql"] retain];
is actually returning where the database is?
The code I use to grab the database from the app directory where kFilename is the database file is:
- (NSString *)dataFilePath{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
return [documentsDirectory stringByAppendingPathComponent:kFilename];
}
and then to use it I do:
if(sqlite3_open([[self dataFilePath] UTF8String], &database) != SQLITE_OK){
This works on both my iPod touch and the iPhone simulator.
EDIT2::
I've just used your above method and it seems to work here - I know it sounds stupid but have you tried rebooting? Its possible something strange is happening with the simulator