*** Assertion failure in -[AppDelegate createDatabaseExecutableFile] - objective-c

Question

I have application and in application delegate i have code for copy the db file into document folder but it's not working i don't know why because it was working before, and giving following error, please take a look and hope you can find something. Thanks
// Creates a writable copy of the bundled default database in the application Documents directory.
- (void) createDatabaseExecutableFile {
// First, test for existence.
BOOL _successDB;
BOOL _successConfig;
NSFileManager* _fileManager = [NSFileManager defaultManager];
NSError* _error;
NSArray* _paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString* _documentsDirectory = [_paths objectAtIndex:0];
NSString* _writableDBPath = [_documentsDirectory stringByAppendingPathComponent:#"turfnutritiontool_ver.db"];
NSString* _writableConfigPath = [_documentsDirectory stringByAppendingPathComponent:#"Configuration.plist"];
_successDB = [_fileManager fileExistsAtPath:_writableDBPath];
_successConfig = [_fileManager fileExistsAtPath:_writableConfigPath];
if (_successDB && _successConfig) {
return;
}
// The writable database does not exist, so copy the default to the appropriate location.
NSString *defaultDBPath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:#"turfnutritiontool_ver.db"];
NSString *defaultConfigPath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:#"Configuration.plist"];
_successDB = [_fileManager copyItemAtPath:defaultDBPath toPath:_writableDBPath error:&_error];
_successConfig = [_fileManager copyItemAtPath:defaultConfigPath toPath:_writableConfigPath error:&_error];
if (!_successDB || !_successConfig) {
NSAssert1(0, #"Failed to create writable database file with message '%#'.", [_error localizedDescription]);
}
}
This is the error:
2012-04-02 13:52:01.162 TurfNutritionTool_ver_5.1[2379:b903] *** Assertion failure in -[AppDelegate createDatabaseExecutableFile], /Development/TurfNutritionTool_IOS_5.1/TurfNutritionTool/AppDelegate.m:188
2012-04-02 13:52:01.165 TurfNutritionTool_ver_5.1[2379:b903] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Failed to create writable database file with message 'The operation couldn’t be completed. File exists'.'
*** Call stack at first throw:
(
0 CoreFoundation 0x0179a5a9 __exceptionPreprocess + 185
1 libobjc.A.dylib 0x018ee313 objc_exception_throw + 44
2 CoreFoundation 0x01752ef8 +[NSException raise:format:arguments:] + 136
3 Foundation 0x011fc3bb -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 116
4 TurfNutritionTool_ver_5.1 0x00003fef -[AppDelegate createDatabaseExecutableFile] + 831
5 TurfNutritionTool_ver_5.1 0x00003486 -[AppDelegate application:didFinishLaunchingWithOptions:] + 86
6 UIKit 0x009f9c89 -[UIApplication _callInitializationDelegatesForURL:payload:suspended:] + 1163
7 UIKit 0x009fbd88 -[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] + 439
8 UIKit 0x00a06617 -[UIApplication handleEvent:withNewEvent:] + 1533
9 UIKit 0x009feabf -[UIApplication sendEvent:] + 71
10 UIKit 0x00a03f2e _UIApplicationHandleEvent + 7576
11 GraphicsServices 0x01e21992 PurpleEventCallback + 1550
12 CoreFoundation 0x0177b944 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 52
13 CoreFoundation 0x016dbcf7 __CFRunLoopDoSource1 + 215
14 CoreFoundation 0x016d8f83 __CFRunLoopRun + 979
15 CoreFoundation 0x016d8840 CFRunLoopRunSpecific + 208
16 CoreFoundation 0x016d8761 CFRunLoopRunInMode + 97
17 UIKit 0x009fb7d2 -[UIApplication _run] + 623
18 UIKit 0x00a07c93 UIApplicationMain + 1160
19 TurfNutritionTool_ver_5.1 0x00002ddd main + 125
20 TurfNutritionTool_ver_5.1 0x00002d55 start + 53
21 ??? 0x00000001 0x0 + 1
)
terminate called throwing an exception(lldb)

Answer 1

It says "file exists". Isn't that enough of a clue?
From the NSFileManager docs:
If a file with the same name already exists at dstPath, this method aborts the copy attempt and returns an appropriate error.
By the way, you should check the error after each copy, not once at the end because if an error occurs on the first copy, and the second copy, you'll lose the error information from the first copy.