Question

so I want to convert NSString to double. I found the following example:

NSString * s = @"1.5e5";
NSLog(@"%lf", [s doubleValue]);

It works but if doubleValue cannot convert the string to double it simply returns 0.0 which is not what I need. I need some method that tries to convert a string representation of double to double and if indicate somehow if it can’t be converted.
c# has an excellent method

double d;
boolean Double.TryParse(str, out d)

Is there any method similar to the above one in Objective C? or maybe it’s better to use regex? however, i don’t really know how to do that.

Answer 1

You can use the NSScanner class:

NSString *s = @"1.5e5";
NSScanner *scanner = [NSScanner scannerWithString:s];
double d;
BOOL success = [scanner scanDouble:&d];

If you want to ensure that the entire string has been scanned (no extra characters after the number), use

BOOL isAtEnd = [scanner isAtEnd];