FMDB not inserting into DB

问题

I am trying to use FMDB to insert a few queries into the DB.
When I check the query for insert it is saying that it is inserting.
Later I can actually read the data from the Tables.
But what happens is that if I try to read the information from the DB, it comes back as null.
When I checked the DB in the Xcode Project, not seems to have updated.
It kind of confusing me. Any suggestion what the problem could be?

回答1:

Your code is wrong. This is what I use to write:

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *dbPath = [documentsDirectory stringByAppendingPathComponent:@"db.sqlite"];

FMDatabase *db = [FMDatabase databaseWithPath:dbPath];
[db open];

[db executeUpdate:@"INSERT INTO foo (bar) VALUES (?)", bar];

[db close];

And to read:

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *dbPath = [documentsDirectory stringByAppendingPathComponent:@"db.sqlite"];

    FMDatabase *db = [FMDatabase databaseWithPath:dbPath];
    [db open];

    NSMutableArray *bar = [[[NSMutableArray alloc] init] autorelease];

    FMResultSet *s = [db executeQuery:@"select * from foo"];
    while ([s next]) {

        [bar addObject:[s stringForColumn:@"bar"]];

    }

    NSLog(@"%@", bar);

    [db close];

Also checkout where I located the db. I think doing your way will work on simulator but not on the device because of sandboxing and all.

Good luck!

EDIT:

Put this in your app delegate:

- (void)createEditableCopyOfDatabaseIfNeeded {


    // 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:@"db.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:@"db.sqlite"];
    success = [fileManager copyItemAtPath:defaultDBPath toPath:writableDBPath error:&error];
    if (!success) {
        NSAssert1(0, @"Failed to create writable database file with message '%@'.", [error localizedDescription]);
    }
}

And run that method from application:didFinishLaunchingWithOptions with:

[self performSelector:@selector(createEditableCopyOfDatabaseIfNeeded) withObject:nil];

Be sure that you put your database in your projecttree first.

来源：https://stackoverflow.com/questions/7050105/fmdb-not-inserting-into-db