How to create a random float in Objective-C?

Question

I\'m trying to create a random float between 0.15 and 0.3 in Objective-C. The following code always returns 1:

int randn = (random() % 15)+15;
float pscale =         


        

Answer 1

1. use arc4random() or seed your random values

2. try

   float pscale = ((float)randn) / 100.0f;
   

Answer 2

Using srandom() and rand() is unsafe when you need true randomizing with some float salt.

On MAC_10_7, IPHONE_4_3 and higher you can use arc4random_uniform(upper_bound)*. It allows to generate true random integer from zero to *upper_bound*.

So you can try the following

u_int32_t upper_bound = <some big enough integer>;

float r = 0.3 * (0.5 + arc4random_uniform(upper_bound)*1.0/upper_bound/2);