How do I generate random numbers on iOS?

Question

What is the best way to generate random numbers using Objective-C on iOS?
If I use (int)((double) rand() / ((double)(RAND_MAX) + (double) 1) * 5.0) to generate a number from 0 to 4, every time I start the program on the iPhone it generates the same numbers to start off with.

Answer 1

There is a very similar question here on StackOverFlow . Here is one of the better solutions (no need for seeding):

int r = arc4random() % 5;

Answer 2

i use

#define RANDOM_SEED() srandom(time(NULL))
#define RANDOM_INT(__MIN__, __MAX__) ((__MIN__) + random() % ((__MAX__+1) - (__MIN__)))

so you can give a min and max

Answer 3

您应该使用当前时间为随机数生成器播种。

srand(time(0));

Answer 4

How random do you need? If you want random enough for crypto, then use SecRandomCopyBytes().

Answer 5

在程序开始时调用srand() ，它将重置随机数生成器

Answer 6

随机数生成的简单功能：

int r = arc4random() % 42;  // generate number up to 42 (limit)