iOS - int (unsigned int) maximum value is 2147483647, unsigned int doesn't work?

Question

the maximum value for an 32-Bit integer is: 2^31-1 = 2147483647. but just with negative and positive number. because the half of the number is negative. so the real maximum value is 2^32-1 = 4294967295. but in this case we just use positive numbers.

ok, a normal int is both negative and positive number. i want to use just positive number because i want the maximum value to be: 4294967295. i'm going to use "unsigned int" instead of "int"

but this will not work! the maximum value is still 2147483647.

here is the code for a simple random number generator:

-(Action for my button) {

unsigned int minNumber;

unsigned int maxNumber;

unsigned int ranNumber;

minNumber=[self.textFieldFrom.text intValue]; //getting numbers from my textfields
maxNumber=[self.textFieldTo.text intValue]; //Should i use unsigned intValue?

ranNumber=rand()%(maxNumber-minNumber+1)+minNumber;

NSString *str = [NSString stringWithFormat:@"%d", ranNumber];

self.label.text = str;

}

and this will view : 2147483647 as a maximum value.

what's wrong? should i use unsigned intValue when i getting numbers from my textFields?

Jonathan

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here you can read about this number. : http://en.wikipedia.org/wiki/2147483647

Answer 1

The problem is intValue which returns a int (not an unsigned int) and is maxed out at 2,147,483,647. If you need larger than INT32_MAX, then use long variables and NSString method longLongValue instead of intValue.

Yes, %d is signed, but if you use %u that will not solve the problem with intValue. Using long long variables and longlongValue method will solve this. For example:

NSString *string = @"2147483650";

unsigned int i = [string intValue];
NSLog(@"i = %u", i); // returns 2147483647

NSUInteger j = [string integerValue];
NSLog(@"j = %u", j); // returns 2147483647

long long k = [string longLongValue];
NSLog(@"k = %lld", k); // returns 2147483650

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So, looking at your original code, it might be:

long long minNumber;

long long maxNumber;

long long ranNumber;

minNumber = [self.textFieldFrom.text longLongValue];
maxNumber = [self.textFieldTo.text longLongValue];

ranNumber = arc4random_uniform(maxNumber-minNumber+1) + minNumber;

NSString *str = [NSString stringWithFormat:@"%lld", ranNumber];

self.label.text = str;