objective-c- selecting items from a database based on a slider value? - sql

Question

I am trying to make a basic app that first brings you to a view controller with a slier, at the moment no matter what the slider value is it selects all from the database but I want the slider value to select all where the price is like the slider value.
I added this line to my code:
NSString *sql = [NSString stringWithFormat:#"select * from carPrices where price = %f", slider.value];
but it does not work, I get the error:
implicit conversion of an objective c pointer to 'const char*' is disallowed with ARC
I previously had the line saying const char *sql instead,
Please if anybody knows what I could be doing wrong could they please give me some advice.
EDIT
Ok so I managed to fix the error by adding this line:
NSString *SQLSTMNT = [NSString stringWithFormat:#"select * from carPrices where price = %f", slider.value];
const char * sql =[SQLSTMNT UTF8String];
but as the prices are very specific is there any way to get it to select prices like the one you chose?
Thanks,
MB.

Answer 1

Float values are hard to work with.
You cannot reliably check if two values are the same, so where price = %f is going to fail.
Instead, you need to do check a range of values:
CGFloat min = slider.value - 0.1;
CGFloat max = slider.value + 0.1;
NSString *sql = [NSString stringWithFormat:#"select * from carPrices where price > %f and price < %f", min, max];