How to check if file saved successfully in objective-c - ios

Question

In my app i use the below code to wirte a .db file to Documents Directory and then want to use it
[NSURLConnection sendAsynchronousRequest:request
queue:[NSOperationQueue mainQueue]
completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
NSString *str = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSLog(#"%#",str);
NSMutableDictionary *retval = [json objectWithString:str];
if ([[retval objectForKey:#"Success"] boolValue])
{
NSString *downloadedData=[[retval objectForKey:#"Value"] objectForKey:#"SqLiteFileArray"];
NSData *mydata=[NSData dataWithBase64EncodedString :downloadedData];
NSArray *paths=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentDir=[paths objectAtIndex:0];
NSString *documentFile=[documentDir stringByAppendingPathComponent:#"4_program.db"];
NSString * yourAppendingText=[[NSString alloc]initWithData:mydata encoding:NSUTF8StringEncoding];
[yourAppendingText writeToFile:documentFile atomically:YES encoding:NSUTF8StringEncoding error:nil];
NSLog(#"finish");
//[self getfile];
//NSLog(#"data %#",downloadedData);
}
else
{
NSLog(#"aaa");
}
self.view.userInteractionEnabled = TRUE;
}];
in nslog i see the finish statement so i thought the file written successfully
but when i re-enter to the app and check if file exists in documents directory it says it is not there
this is my file exists code:
NSString *docsDir;
NSString *realpath;
NSArray *dirPaths;
dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
docsDir = dirPaths[0];
realpath=[[NSString alloc] initWithString:
[docsDir stringByAppendingPathComponent: #"4_program.db"]];
NSFileManager *filemgr = [NSFileManager defaultManager];
if ([filemgr fileExistsAtPath: realpath ] == NO)
{
NSLog(#"no file");
}
else
{
NSLog(#"file found");
[self getdata];
}
am i missing something? how can i learn file written successfully finished?

Answer 1

i changed to my writeToFile to
[[NSFileManager defaultManager] createFileAtPath:documentFile
contents:mydata
attributes:nil];
and now it works and everything is ok