- (NSInteger) fieldDecimal: (NSInteger) fieldno;

The function fieldDecimal() returns a length of a fractinal part of a field by index.
It is suitable only for Numeric, Float, Double fields. For other types it returns 0.
It also returns 0 if index is out of range.

    // your code
    for (NSInteger i=0; i < [dbf fieldCount]; i++)
        NSLog(@"%ld", [dbf fieldDecimal:i] );
    // your code