Unable to connect SQLite Database in iOS

问题:

I am completely new to SQLite and iOS. I am following a basic tutorial on how to use SQLite in iOS:

http://www.switchonthecode.com/tutorials/using-sqlite-on-the-iphone#comment-11617

In the above link, they have specified the database as:

sqlite3 *database;

int result = sqlite3_open("/myExampleDatabase.db", &database);

but when I use the above code with replacing my database name, I get an error as specified in the subsequent alertview.

My question here is, do I have to add the database file into my resource folder? If not, do I have to have my database file somewhere that is accessible to iOS?

回答1:

I suggest using FMDB wrapper for SQLite: https://github.com/ccgus/fmdb

回答2:

If you want to open a sqlite database, you might want to:

1. Make sure you're including your database in your bundle.

2. Programmatically copy the database from your bundle to your documents (esp important if user will be modifying the database; if you're only reading, you could go ahead an just open the version in the bundle).

3. If you're running this in your simulator, you can go ahead and inspect the bundle and Documents folders if things don't go right, just to make sure everything is where it should be. You simulator's folder is something like "~/Library/Application Support/iPhone Simulator/5.1/Applications/" (replace the 5.1 with whatever version of your simulator you are using). You might have to unhide your Library folder, if you haven't already, by running the chflags nohidden ~/Library in a Terminal command-line window.

So, the code for getting the path of the database (and copying it to the Documents if it's not there yet), might look like:

NSString *databaseName = kDatabaseName; // obviously, replace this with your database filename, e.g., @"myExampleDatabase.db"

NSString *documentsFolder          = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString *databaseFullDocumentPath = [documentsFolder stringByAppendingPathComponent:databaseName];
NSString *databaseFullBundlePath   = [[NSBundle mainBundle] pathForResource:databaseName ofType:@""];

NSFileManager *fileManager = [NSFileManager defaultManager];
if (![fileManager fileExistsAtPath:databaseFullDocumentPath])
{
    NSAssert([fileManager fileExistsAtPath:databaseFullBundlePath], @"Database not found in bundle");

    NSError *error;
    if (![fileManager copyItemAtPath:databaseFullBundlePath toPath:databaseFullDocumentPath error:&error])
        NSLog(@"Unable to copy database from '%@' to '%@': error = %@", databaseFullBundlePath, databaseFullDocumentPath, error);
}

Then, if you're doing your own sqlite calls, it would be something like:

sqlite3 *database;
if (sqlite3_open_v2([databaseFullDocumentPath UTF8String], &database, SQLITE_OPEN_READWRITE, NULL) == SQLITE_OK)
{

    // do whatever you want to do
}

Or, alternatively, if you're using FMDB, it would be something like:

FMDatabase *db = [[FMDatabase alloc] initWithPath:databaseFullDocumentPath];
NSAssert(db, @"Unable to open create FMDatabase");
BOOL success = [db open];
NSAssert(success, @"Unable to open database");
if (success)
{
    // do whatever you want to do
}

回答3:

I fully support the previous answer in most cases, however:

Are you sure you have to use sqlite3 instead of Core Data?

There are several discussion where you can get information when to use a database wrapper (like fmdb) and when to use Core Data. (Speaking personally, I love to use fmdb, but it always results in more code, complexity and most of the time a worse performance)

• Core Data vs SQLite 3
• Use CoreData or SQLite on iPhone?
• Core Data vs Sqlite and performance
• Core Data vs SQLite 3
• is it worth using core data for a simple sqlite app on the iphone with one table and no relationships or complicated subtable/views?
• Core Data vs. SQLite for SQL experienced developers

Some links to get started with Core Data:

• Core Data Programming Guide (Apple)
• Core Data Tutorial for iOS (Apple)