I can't trap FMDB empty resultset

Question

I am having trouble trapping an empty result set from FMDB. The code is below. I am getting NSLog's from the database opening and closing and NSLog "1" but none of the ones in the If statement! If I have data in the database its fine, but I want to trap and edit result if the database is empty.

    [self openDatabase];

NSNumberFormatter *nfcurrency = [[NSNumberFormatter alloc]init];
[nfcurrency setNumberStyle:NSNumberFormatterCurrencyStyle];
[nfcurrency setLocale:[NSLocale currentLocale]];

FMResultSet *result = [[self getDatabase]executeQuery:@"SELECT BFNeeded FROM tblBets ORDER BY pk DESC LIMIT 1,1;"];
//FMResultSet *result = [[self getDatabase]executeQuery:@"SELECT BFNeeded FROM tblBets ORDER BY pk DESC LIMIT 1,1;"];
NSLog(@"1");
if (result == NULL) {
    NSLog(@"Last BFNeeded Result = nil");
} else {
    while ([result next]) {
        NSLog(@"HERE");
        NSString *lastBFNeeded = [nfcurrency stringFromNumber:[NSNumber numberWithDouble:[result doubleForColumn:@"BFNeeded"]]];
        NSLog(@"lastBFNeeded=%@",lastBFNeeded);
    }
}

NSLog(@"ClosingDB");
[self closeDatabase];

Continuing after getting first reply:

I can't get hasAnotherRow to work as expected. I have this code:

FMResultSet *result = [[self getDatabase]executeQuery:@"SELECT BFNeeded FROM tblBets ORDER BY pk DESC LIMIT 0,1;"];

if (result == nil) {
    NSLog(@"Last BFNeeded Result = nil");
}
else {
    NSLog(@"has results1: %@", [result hasAnotherRow] ? @"YES" : @"NO");
    while ([result next]) {
        NSLog(@"has results2: %@", [result hasAnotherRow] ? @"YES" : @"NO");
    }
}

With a database that returns a result, I get result1 NO, result2 YES so I assume the hasAnotherRow must go inside the while ([result next]) loop. However with an empty database, I get result1 NO and it doesn't even get to result2!

score 6 · Accepted Answer · edited May 23 '17 at 11:44

6

the "result" will never be nil for a query that produces 0 rows.

also, you shouldn't compare object pointers to NULL -- compare to nil. See this question: NULL vs nil in Objective-C

try this:

FMResultSet *result = [[self getDatabase]executeQuery:@"SELECT BFNeeded FROM tblBets ORDER BY pk DESC LIMIT 1,1;"];

NSLog ( @"has results: %@", [result hasAnotherRow] ? @"YES" : @"NO" );

edited May 23 '17 at 11:44

Community

1
1

answered Dec 14 '11 at 21:22

TomSwift

39,369
12
121
149

Many Thanks. I didn't know of hasAnotherRow. – Darren Dec 15 '11 at 13:02
I can't get this to work as expected. More info above. Thanks – Darren Dec 15 '11 at 17:52
You're just going to have to call [result next] once up front and see if it returns nil or not. – TomSwift Dec 15 '11 at 18:19
Thanks, I'm still a beginner to C but learning fast. I took the while loop out and just used [result next] and its working now. Thanks – Darren Dec 15 '11 at 18:34

Nickedg · Answer 2 · 2015-05-29T13:53:35.100

0

NSInteger count;

query=[NSString stringWithFormat:@"select Count(*) from %@  where name = 'brandon' ",dbName];
results = [database executeQuery:query ];
while([results next]) {
    count  = [results intForColumnIndex:0];
    NSLog(@"count:%d",count);
}

will set count equal to zero if there is no entry

edited May 29 '15 at 13:53

answered May 29 '15 at 00:58

Nickedg

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2

I can't trap FMDB empty resultset

2 Answers2