NSString is integer?

Something like this:

NSScanner* scan = [NSScanner scannerWithString:toCheck]; 
int val; 
return [scan scanInt:&val] && [scan isAtEnd];

You could use the -intValue or -integerValue methods. Returns zero if the string doesn't start with an integer, which is a bit of a shame as zero is a valid value for an integer.

A better option might be to use [NSScanner scanInt:] which returns a BOOL indicating whether or not it found a suitable value.